Found Chem (2014) 16:107–123 DOI 10.1007/s10698-013-9178-0
Structured system in chemistry: comparison with mechanics and biology Giovanni Villani
Published online: 9 January 2013 Springer Science+Business Media Dordrecht 2013
Abstract The fundamental concept of structured chemical system has been introduced and analysed in this paper. This concept, as in biology but not in physics, is very important in chemistry. In fact, the main chemical concepts (molecule and compound) have been identified as systemic concepts and their use in chemical explanation can only be justified in this approach. The fundamental concept of ‘‘environment’’ has been considered and then the system concept in mechanics, chemistry and biology. The differences and the analogies between the use of the systemic approach in these disciplines have been analyzed and correlated to the general problem of reductionism and complexity perspectives. The inanimate–animate dichotomy can be reconsidered in this new approach. Since the chemical systemic concepts of molecule and compound can be dated to the nineteenth century, chemistry can be considered the first true systemic science and its historical evolution can be a model for other sciences (such as the humanities) where the systemic concepts are important. Keywords Structured system Systemic approach Chemistry versus mechanics Chemistry versus biology Inanimate–animate dichotomy
Introduction The system concept has two meanings in science. This term refers to a piece of reality in study and no relationship exists between it and the concepts of organization and structure into mechanics and thermodynamics. In other areas, such as in living systems, the system concept means an entity structured or organized. For the purpose of this article, ‘system’ denotes a structured/organized entity. In general, there is a difference between the two fundamental concepts of organization and structure, but we do not discuss it here, since only the last is used in chemistry. We will use the explicit diction of ‘‘structured system’’ G. Villani (&) Istituto di Chimica dei Composti OrganoMetallici (ICCOM), UOS Pisa, Area della Ricerca del CNR, Via G. Moruzzi, 1, 56124 Pisa, Italy e-mail:
[email protected]
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(as in the title of this paper) only when the meaning of the ‘‘system’’ term can generate errors. The system concept is present in all scientific disciplines. However, this concept acquires greater importance passing from physics to chemistry, from chemistry to biology until the social sciences where the importance of this concept is well established. In this point of view, chemistry plays an essential role: it is the first systemic science and the main purpose of this paper is to demonstrate and underline this statement and explain its consequences. It is not accidental that biology, where the system concept is widely used, using more chemical concepts to physical concepts in their explanations. Physics, in fact, with its ‘‘insistence’’ on the universal natural laws, is able to study mainly general characteristics (e.g. the energy or the movement) that the specific characteristics of an entity. Contrary, individuality is essential in system concept. This is evident in ‘‘species’’ concept, absent in physics and present in chemistry and biology. The system concept is also important for the overall image and meaning of science. Two different approaches have been used in philosophy of science: the reductionism and the holism. In the first approach, one assumes (directly or indirectly) that the complexity of world is only apparent and the reality is in ‘‘deep’’ (both conceptual and material) simple. A good example of this approach may be the old atomic theory, that of the Greek philosophers Leucippus and Democritus. The main point of these authors is as follows: all things are aggregates (more or less stable, but not indivisible) of indivisible parts (atoms), countless, eternals, immutable, without parts or internal movements. Atoms are fragments of a single entity, the ‘first stuff’, and differ each other only in the quantitative amount of the largeness, form, position and movement, without any qualitative difference. One of the principal goal of these philosophers is, in fact, the reduction of qualitative characteristics of the objects in measurable quantities. Many centuries after, at the birth of modern science (and mainly of physics), Galileo says1 : Che ne’ corpi esterni, per eccitare in noi i sapori, gli odori e i suoni, si richiegga altro che grandezze, figure, moltitudini e movimenti tardi o veloci, io non lo credo; e stimo che, tolti via gli orecchi le lingue e i nasi, restino bene le figure i numeri e i moti, ma non gia` gli odori ne´ i sapori ne´ i suoni, li quali fuor dell’animal vivente non credo che sieno altro che nomi. In the reductionist perspective, the concept of structured system is completely absent since the structure, as global property, is not reducible to the elementary parts of the system and their interactions. In contrast is the holistic idea of reality. This point of view has always been minority in science and has been identified with different terms: holistic, notreductionist, complexity, and so on. The basic idea of this worldview is: ‘‘the whole is greater than the sum of its parts’’. This sentence is ambiguous (Nagel 1971, pp.140–163) and was considered2 ‘‘un po’ irritante e un po’ idiota’’ (Ageno 1986, p.100), but is evocative of an important feature of systems: it is possible to divide the system in parts and with these and their interactions to obtain information about it, but in this analytic and then synthetic operation one looses something, it is not possible to retain all original 1
G. Galilei, Il Saggiatore, Edizione nazionale delle opere, vol. 6, Barbera, Firenze 1968, p. 350, in (Bellone 1999, p. 43), (my translation) ‘‘To excite in us tastes, odors and sounds I believe that noting is required in external bodies except shapes, numbers, and slow or rapid movements; and I think that if ears, tongues and noses were removed, shapes, numbers and motions would remain, but not odors or tastes or sounds that, out of the living beings, I believe the latter are nothing more than names’’.
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(my translation) ‘‘a bit irritating and a bit idiot’’.
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characteristics of this entity. With words of Jacob, the organization possesses properties that do not exist in the lower level and that3 ‘‘possono essere spiegate in base alle proprieta` dei costituenti, ma non dedotte da essi’’ (Jacob 1971, p. 376). A good example, generally accepted, is the lost of ‘‘life’’ property when a living system is dissected. This, which is evident in biological context, is a general feature of the system concept in our opinion. The fundamental concepts of molecule and chemical compound (in microscopic and macroscopic world, respectively) are not needed in a correct reductionist perspective, since both are ‘‘aggregates’’ of atoms and elements, the only fundamental entities. Here (and in chemistry we can do) is neglected, obviously, that the atoms are not the elementary particles and also the elements are not so elementary. It makes no sense insert a level, conceptual before physical, between the microscopic world of atoms and the macroscopic world of elements in the correct reductionist idea, like there is no conceptual level of aggregates of molecules. In this point of view, in fact, the molecules are only the ‘‘aggregates’’ of atoms and no specific role has attached to these entities. The existence of a molecular level can be justified only if a molecule ‘‘is not an atomic aggregate’’, but ‘‘is an atomic system’’, a structured piece of world, which leads the emergence of ‘‘new’’ properties. In absence of the systemic approach in science, and in chemistry in particular, the concepts of molecule and chemical compound are meaningless and should only be used as working concepts.
System in science Before to analyse the system concept in various disciplines, we will discuss a general question of the system concept in science (and beyond): all systems are inserted in a context, in an environment. System and environment The environment in science is the context from which the system is separated, all different things from system. Clearly, since the system is a small part of universe, its environment, defined as the complementary part, is very large and can be practically equivalent to the whole universe. This definition is impracticable and unnecessary. The environment is then defined as the part of universe important for the properties and phenomena of this specific system and that can be modified by the system and its processes. Some times, the last part of this definition, the environment modification due to the system, is neglected and only the influence of environment on system is considered. In general, the individualisation of the environment, and the specification of its interactions with system, is an essential part of modelling the system in study. There are also cases in which environment must be considered a system and, consequently, we have a small system in study incorporated in a larger system (its environment). This is not unusual, since the universe can be divided into several interacting levels, each with its own systems, in the complexity perspective. This does not automatically imply a hierarchy relationship among these systems, but only the necessity of including explicitly systemic interaction between the system in study and its structured environment. This is the case of the biological world for example, where the interaction between the system and its environment is cyclic and of great importance. In this case, also the definition of 3
(my translation) ‘‘can be explained based on the properties of the constituents, but not deducted by them’’.
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environment is strictly related to its system. The biological concept of ‘‘living space’’ of an organism may be an example. In this last case, the environment is defined as an entity conditioned from the ‘‘needs’’, ‘‘stimulus’’ or ‘‘goals’’ of the organism and hence from its sensorial apparatus (Simon 1956), since the system must know its environment if has to adapt to it. In other cases, it is not important to describe in details the environmental characteristics and the structure of the environment can be neglected. For example, in quantum chemistry it is first studied the isolated molecule and then its molecular states are perturbatively changed a posteriori, as a result of the nonspecific interactions of this molecule with the environment. There are two extreme positions in relationship between the system and its environment: an ecological position, where the system is ‘embedded’ in its environment and a second that considers the environment like a noise, casual, without structure and with no specific dependence from the system. The choice of the first or second position characterizes in different way both the system and environment and also gives substantial differences in people that works in the ambit of complexity. For example into the autopoietic idea of Maturana and Varela, scientists that work certainly in the complex perspective, the environment is underestimated in our opinion (Villani 2008, Chap. 8). The role of the environment and its relationship with system are very important for us: the system can remain in a steady state, different from the equilibrium state, only by the help of this relationship and this interaction can generate the order, the main paradox of the mechanical approach. The ‘‘steady state’’ concept is very important in the systemic framework and is the main feature in differencing between the ‘open’ and ‘closed’ system. On the other hand, it is not possible to use the ‘‘closed system’’ model in biological and social studies, since the importance of material, energy and information flux from the system to the environment, and in the opposite direction, can not be eliminated in these cases. The concept of ‘mechanical system’ (Villani 2005) One of the main goals of this paper is to compare the use of the system concept in physics and in chemistry. Here we will focus only on mechanics, but equally interesting would be the comparison between the use of the system concept in thermodynamics and chemistry. Even in thermodynamics, as in mechanics, in fact the concept of system does not imply in any way the concept of structure and/or organization, but thermodynamics, unlike mechanics, can not be framed in the classical atomist perspective and reductionist. It would be needed, hence, a detailed discussion to highlight the similarities and differences between mechanics, thermodynamics and chemistry in the use of such concepts, but such discussion is outside the scope of this paper. In order to specify the definition and characteristics of the mechanical system concept, we must highlight the meaning of the system term in mechanics. First of all, we must assume that a physical entity is defined and absolutely divided from its processes, despite the general problems in this definition and separation (Toraldo di Francia 1994, pp. 33–40). Then, we can definite the term ‘system’ like synonymous of the term ‘entity’, since the system concept does not include any additional characteristic (like the structure or the organization) in mechanics. Consider a physical entity, separate from its environment, with time-dependent characteristics. The complete separation of this part of world, the assumption of absolutely isolated system, is impossible of course, but this approximation is usually used in mechanics. In this discipline a system is completely described by ‘n’ values of the observable physical quantities. This set can be divided in two groups: the ‘m’ properties
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approximately constant in the range of time in study and the ‘n-m’ other physical properties, that change considerably in this time range. The first ‘m’ properties are named ‘system variables’ and they define and describe the system in investigation; the second, named ‘configuration (or state) variables’ of the system, describe the system state at a time. The separation in system and its state is strictly related to time range considered (in general all properties change, although not all with same speed (Villani 2001, Chap. 8)) and to the measurement accuracy, hence to the experimental tools used to measure these properties. The number of state variables (‘n-m’ in our case) is by definition the number of the ‘freedom degrees’ of this system and is univocally determined in a mechanical system. The physical properties describing these freedom degrees are in general not specified. They are named ‘generalized coordinates’ of a particular space, named ‘configuration space’. This space is essentially static and can be used only to describe the equilibrium states of system. If one defines also the ‘generalized velocities’, the time derivative of generalized coordinates (even theirs in number of ‘n-m’), one can define a ‘phase space’ (of dimension ‘2n-2m’). In summary, in classical mechanics an isolated physical system is an entity univocally determined from its dynamical state at any time, which means, among other things, that the system state is perfectly identified at any time and can be obtained from the solutions of time-dependent equations and from the set of coordinates and velocities (canonical variables) of the initial state. In conclusion, the dynamics of a system depends from the set of state variables and from its dimension and, hence, from the degree of abstraction and simplification included in the model, and from the properties assumed constants, for the purposes of this specific study. It was Hamilton in nineteenth century, who formulated the dynamical problem in this abstract way. In mechanics there are only two energy forms: kinetic and potential. The kinetic energy is related to the generalized velocities, and can be always expressed in quadratic form; the potential energy, contrary, is related to the generalized coordinates, and can assume various mathematical forms. The sum of the kinetic and potential energy is the total energy of the system and must be preserved in closed system. In the Hamilton formalism, the energy of the system (Hamiltonian) plays a key role. In fact, the energy in canonical variables is left unchanged from all change of variables (canonical transformations). The Hamiltonian of the system allows to express the evolution of canonical variables in 2(n-m) first order differential equations. From the nineteenth century to now, the efforts of the scientists were primarily focused on the identification of the dynamical problems that may be resolved in this way, in order to obtain the calculation of the trajectories in the phase space. An important point to emphasize is the substantial difference between the kinetic energy and potential energy into mechanics. While the first can be always written as the sum of contributions, each one related to a single degree of freedom, this is not always true for the potential energy. In fact, if both energy forms could always be written as the sum of contributions of n-m degrees of freedom, one would n-m independent dynamical equations in all cases and would apply a conservation energy principle for each degree of freedom. In this case, the exchanges between the different degrees of freedom would not possible and the system could be described with n-m non-interacting degrees of freedom. Vice versa, a not decomposable (in coordinates) potential energy will constitute a ‘‘common bath’’, through which the different degrees of freedom will be able to exchange the kinetic energy, as final result. In the integrable systems (sub-class of the dynamical systems) there is a set of canonical transformations with the effect of eliminating the potential energy terms related to two different coordinates. All energies of the system are then attributable to opportune ‘‘free particles’’ of system, particles defined by this canonical transformation.
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Such particles are not interacting in this description and, therefore, move (have only kinetic energy) in an independent way. This means that the system can be divided in ‘‘really’’ independent entities and the interactions are only illusions when only the mechanical perspective is assumed and only two energy forms are possible. Hence, the assumption of the pure mechanical scheme generates a description in terms of independent entities, each one with its evolution. In our opinion, the lack of the internal structure of parts, with its internal energy, invalidates a completely mechanical picture (Villani 2008, Chap. 6). The Hamiltonian formulation of dynamics clearly shows an essential characteristic of conservative system (constant energy): its complete determination from the initial conditions, its essentially static and deterministic evolution. These trajectories, in fact, describe the complete history (past, present and future) of our points and, hence, the evolution of system is completely determined and determinist. Chemical systems The aim of this paragraph is to show the system concept (defined as structured and/or organized entity) in chemistry and emphasize the differences and similarities with the mechanical system just considered. Chemistry works on two levels: the macroscopic of pure substances (elements and compounds) and the microscopic of atoms and molecules. We will develop the chemical system concept in both levels, as a consequence. In particular, we will concentrate ourselves on the concepts of chemical compound (macroscopic level) and molecule (microscopic level). The concept of molecule opens the question of the reduction of chemistry to quantum mechanics, of course. This is an important subject considered in literature (Scerri 2007; Vihalemm 2010), but not explicitly analyzed here. Differently from physics, both these chemical systems carry out a fundamental role in this discipline, shaping, therefore, chemistry as the first true systemic science and proposing this discipline as a particular way of looking to the material world (inanimate and animate) in a non-reductionist and pluralist perspective. In fact, even before considering the system concept in biology, the general vision that comes from material world is articulated in a reductionist and a systemic approach, in a ‘simple’ physical perspective and a ‘complex’ chemical one. From the cultural and philosophical point of view, the specific characteristic of the chemical approach is a qualitative rich world: its entities (molecules and compounds), millions, are different each other, different enough to deserve a specific name. This characteristic makes chemical approach capable of explaining the complex macroscopic inanimate world, full of objects with different qualities, and, the still more complex, living world. Even in strictly scientific point of view, the complexity levels of molecules and of chemical compounds have a particular characteristic: they are the step before the bifurcation between the inanimate and animate world. Compared to living world, the molecules and compounds are the immediately preceding complexity levels and are therefore fundamental in its study, as demonstrated by biochemistry. They are, however, even the immediately preceding levels of the macroscopic inanimate objects (as the rocks, for example) and the molecule and compound can become their referent of explanation, as evidenced by geochemistry. Now, let’s start from macroscopic level and then continue with microscopic level, following a historical and epistemological method. One key point in the genesis of the modern chemical compound concept was to overcome the idea that these substances had closely related to the ‘methodology’ of obtaining and, therefore, they were of countless number. To first view, it seems strange that the modern element concept is due to an increase of number of these entities (from the four elements of Aristotle to the thirty-three
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of Lavoisier) (Villani 2008, pp. 166–168) and the chemical compound concept to a decrease of this number (from countless to many). In reality, reductionist idea needs few elements and implies a countless number of compounds, since these lasts are mixtures of elements without creating new entities. The systemic idea, instead, presupposes in each complexity level an intermediate number of entities between ‘‘few’’ and ‘‘countless’’ (Villani 2001, Conclusion). Returning to the countless number of chemical compounds, this idea, alchemical before chemical, was an obstacle to remove in order to reach the modern chemical view. In seventeenth and eighteenth century almost all chemists reasoned according to reductionist perspective. For example, in 1,706 W. Homberg in his Essays de chimie said that since the substance of a composed body was formed exclusively with the assembly of material components, if this assembly was changed by grouping the parts in a different way, since these possibilities were in a countless number, it was evident a continuum change of the substance. In addition, Homberg believed that the facts of the chemical reactions gave rise to a continuous and endless series of different compounds4 : La materia della luce producendo le materie solforose, s’introduce nella sostanza dei corpi, ne cambia l’arrangiamento delle parti e le aumenta, e di conseguenza cambia la sostanza stessa di questi corpi in tutti i modi in cui essa puo` differentemente collocarsi e in quantita` differente, la qual cosa produce una varieta` infinita; in modo tale che se si volesse paragonare la varieta` delle materie che esistono, a quella che potrebbe esistere per mezzo di tutte le combinazioni possibili, noi saremmo obbligati a dire che l’Universo conosciuto e` ben poca cosa in confronto di cio` che potrebbe essere, e anche se si avessero numerosi Mondi come il nostro, essi potrebbero essere tutti forniti di oggetti differenti senza cambiare la materia, ne´ la maniera in cui questi oggetti sarebbero composti; la qual cosa dimostra una ricchezza ed una potenza infinita dell’Essere che ha prodotto l’Universo. The existence in nature of a continuum of chemical compounds had debased the meaning and importance of the effective compounds obtained experimentally. In fact, these were only related to the historical ability of the chemical experimentation, and thus also their classification were artificial and limited: to be closely related to the reaction conditions had lowered the ontological status of the chemical compounds. In early 1800, there were two opposing views of the chemical compounds, and consequently of theirs number: one of Claude Louis Berthollet and that of Joseph Louis Proust. In 1799, with the Recherches sur le loi de l’affinitte´ and in 1803 with the Essai de statique chimique, Berthollet built his theory of chemical affinities, and here we would like to analyse only the consequences of this theory on the number of chemical compounds. For Berthollet the number of chemical compounds was countless and in particular with the mixture of two reagents could be obtained a countless series of products between two limit values (minimum and maximum) of the ratio of the reagents. The existence of two limit points in a compound of two elements, and therefore the impossibility of countless other 4
W. Homberg, Suite de l’article trois des Essays de chimie, in (Di Meo 2004) (my translation) ‘‘The matter of light producing sulfurous matters, introduces itself in the substance of bodies, changes the arrangement of parts and increases, and consequently changes the real substance of these bodies in all ways in which can differently place itself and in different amount, the which thing produces a countless variety; in such way that if one wants to compare the variety of the matters that exist, with that could exist through all possible combinations, we would be obliged to say that the known Universe is a very insignificant thing in comparison of that could be, and even if numerous Worlds as our could exist, they could be all supplied of different objects without to change matter, neither the way in which these objects would be composed; the which thing demonstrates a wealth and a countless power of the Being that has produced the Universe’’.
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compounds beside the countless possible ones, partially emancipated the chemical compounds from the circumstances of reaction, since there were not compounds available in all circumstances of reaction. As a result of experimental researches, principally about metallic oxides of iron, copper and pond, Proust enunciated his law of the definite proportions, where each chemical compound was constituted with a fixed and constant proportion of components, independently from the experimental conditions in which was formed. The researches of Proust had large success and the law of the definite proportions prevailed on the continuum hypothesis of Berthollet. After Proust’s law, each chemical compound is definitively characterized as a new specific entity. The problem of the correct nomenclature of these compounds was a normal consequence of this law. If the chemical compounds were countless, it would had little sense to look for theirs the names that were not mere labels, but were, so to speak, ‘‘naturals’’. Instead, since each chemical compound had a ‘‘definite proportion’’, it was important to determine its formula and related it to its physical and chemical characteristics. Obviously, the laboratory circumstances, then as now, determine whether or not can be generated this specific compound, but no event can generate a different percentage of constituents for this compound. Moreover, different conditions can give identical compounds, for example a chemical compound synthetically produced or extracted from a natural product. This is evident today, almost natural, and, consequently, it is not considered and appreciated the effort to reach this conclusion, anything but obvious and banal. The consequences of this new concept of compound have been enormous: the entire modern chemistry is structured, at a macroscopic level, on this concept. Here we would like, however, to recall only a consequence, trivial, but not completely absorbed into the modern environmental culture: the difference between a natural and an artificial body. After that the new definition of compound has eliminated the circumstances of formation from the ‘‘nature’’ of the body, such differentiation loses much of its meaning. Let us now consider the microscopic level of chemistry and its central concept of molecule. The molecule concept is relatively modern, although one can find important ancestors, and this is not strange in the reductionist perspective. A matter composed of atomic aggregates (formed in more o less random way) was an idea already present in Democritus, as we have shown. However, nobody had given theirs the names, and these aggregates remained as atomic groups for a long time, whose properties were those of the constituent atoms. In fact, the attribution of the names evidences a new ontological status of these entities with the passage from the aggregates (atomic ensembles) to the molecules (atomic systems). The attribution of a specific name to a portion of matter means to put in evidence its individuality (specific properties) and such molecule can be used as a subject/ object of explanation. The idea of a microscopic world without any specific new entity, generated by the atomic interactions, has its counterpart in the macroscopic world with only a few elements (the four elements of Aristotle) and where only their countless combinations create a matter with its complex appearances. In the classical atomism existed scientific and epistemological obstacles to the definition of an analogous of the modern concept of molecule. In the epistemological point of view, as we have already said, the classical atomism was probably the first coherent reductionist philosophy. In this perspective, the molecule concept was incomprehensible as structured entity (system), distinct from a set of atoms. In the scientific point of view, the atoms of Democritus did not lose their identities in the aggregation process and remained only in mechanical contact. Aristotle criticized atomism because these atoms could not generate new entities in aggregations. On this fundamental point, atomists denied the individuality of composed substance. Aristotle was on this point more near to modern chemical idea: the
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constituents, in forming compounds, generate new substances and not the simple mechanical aggregates of the previous elements. The impenetrability and eternity of the classical atom rendered impossible the modern idea of molecule. Today, in a similar philosophical-scientific picture moves quantum mechanics: the molecule is a set of atoms, an aggregate not a system, and nothing of new is generated putting together a group of atoms. In nineteenth century, the concept of molecule was long confused with the atom concept. At the end of eighteenth century and early nineteenth, the French chemists assigned the term of mole´cule to the limit of divisibility, while the British chemists used the term of atom with same meaning. This confusion, as we have seen, had philosophical roots. From the scientific point of view, part of this confusion came from the difficulties of imagining the molecules of certain elements (hydrogen, oxygen, etc.) formed with more than an atom (H2, O2, etc.). Dalton excluded a bond between two equal atoms. As a consequence of the different meaning (atom or molecule) of the elementary particle, a contradiction between the Dalton and Gay-Lussac hypotheses was found. In 1811, Avogadro tried to remove this contradiction and began to distinguish these two concepts of elementary particle, but his work was for long time misunderstood. One of the first that had clearly understood the indispensability of a clear definition of concepts of atom and molecule, was Gaudin. Having clearly defined these concepts, Gaudin introduced the distinction of monatomic, diatomic and polyatomic molecules in the elementary gases. He wrote that one molecule of hydrogen gas combined with one molecule of chlorine gas gave two molecules of hydrogen chloride gas: for this to happen, it was necessary that the original molecules were divided into two parts and, since these two half-molecules could not be further divided, these parts were considered atoms. For the first time, this author wrote the water synthesis correctly: 2H2 ? O2 = 2H2O, in which clearly the oxygen and hydrogen molecules were diatomic, but even this work did not clarify definitively the situation. In 1848, also Gerhardt tried to clarify the difference between the concepts of atom and molecule. For this author the atom was indivisible, but did not exist in the free state and the molecule was a group of atoms, held together by the attraction of matter, divisible with the normal chemical techniques. The work of Cannizzaro resolved definitively the problem of difference between the atom and the molecule. Basing on the measure of vapour density of the elements and the compounds, using the specific heats for controlling the atomic weights and the isomorphism criterion in order to reveal anomalies in the ‘molecular constitution’, Cannizzaro gave a new system of atomic weights of 21 elements. As consequence of relation of Cannizzaro to the congress of Karlsruhe in 1860 it was accepted the following proposal: it was adopted different concepts for molecule and atom, where molecule was defined as the smallest amount of substance with specific characteristics in the chemical reactions, and atom was defined as the minimum amount of substance found in the molecules of its compounds. The molecule concept carries out a fundamental role in modern science and not only. The subtitle of my book, already mentioned, La chiave del mondo says ‘from philosophy to science: the omnipotence of molecules’. This concept can be used for all material entities and constitutes the main concept of a specific scientific approach to the study of matter: the chemical approach for composition. Such concept, in fact, allows to use the qualitative and quantitative complexities of the macroscopic world and transports theirs in the microscopic world. In this way, the alternative between the microscopic simplicity (one or few microscopic substances) or the complete complexity (countless microscopic substances related to the macroscopic uniform substances, like the wine, wood, etc.) can be avoided.
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The molecular world, with million of different individuals, each one with own name, can represent moreover the connection between the ‘simple’ world of physics and the ‘complex’ biological world and this molecular world can also be used as prototype for the explanation in scientific branches (like the human sciences) that can be organized with difficulties with the law concept, typical of physical approach (Villani 2002). Now we would like to compare the concepts of molecule and mechanical system. Let us consider the following mechanical system: a group of moving balls on a billiard table. The only possible mechanical interaction between the constituents of this system is the collision, instantaneous and in contact interaction, when one neglects the gravitational attraction, obviously. The collisional interaction modifies only the ball velocities in the ideal model of elastic collision. This mechanical system represents the idea of matter of classical atomists: the atoms were perfectly elastic pieces of matter and collide each other in empty space. The velocities of two collided spheres remain correlated to each other after collision, due to the conservation law of momentum (or energy). In order to clarify the concept of correlation, we can say that two variables vA and vB (and their physical systems, A and B spheres) are not correlated when the joint probability of finding the sphere A with vA velocity and the sphere B with vB velocity is the product of probabilities P(vA)P(vB). If the velocity of a ball depends from that of the another with which collided, the joint probability could not be the mere product of probabilities. In the simplest case of two equal balls in collision, A in motion with vA velocity and B at rest, after collision it is obtained A at rest and B with vA velocity. In general, when two bodies (A and B), with vA and vB velocities, collide the resulting velocities will be function of both initial velocities. The property of maintain the correlation after the interaction is not specific of the impact, but is valid for all pairs of interacting systems in past, even if they are not in interaction at present. The correlation among events thus appears as the memory of past events. In this context, we can translate property of homogeneity of time saying that the memory of an event remains unchanged until a new event occurs: the mere passage of time does not alter the memory, which continues to be present as correlations, and a measure of effective isolation of a system can be related to more or less conservation of this memory. If now a sphere A, after hitting the sphere B, will hit a new sphere C, the correlation between A and B goes to C, which will ‘remember’ even the A-B collision. As one might guess, due to the subsequent impacts there is an increase of the correlations, but each one becomes singly weaker. After some time, the velocity of each sphere will be determined by all the myriads previously suffered collisions, while the influence of each collision happened in past will become smaller, to the limit negligible. A similar spread of the correlations happens with all set of objects ‘united’ from an interaction, even different from the collision. According to Prigogine, it is this spread and growth of correlations which physically represents the arrow of time, i.e. its unidirectionality. Recently, an increasing number of experiments seems to confirm a violation of the invariance of the inversion time in meson decay processes (Vaccaro 2011). The theoretical variable appointed to quantify the directionality of time is the entropy, while the energy (or better its conservation) reflects its uniformity. We return now to the question whether our set of balls, arranged in a specific way on a billiard table, represents an organized entity (system) or not. Of course, this ‘piece of world’ has own specific structure, if one assumes for ‘‘structure’’ the set of the defined positions in space. The structure concept in material bodies certainly implies the spatial arrangement of constituent parts, but this concept can not be limited to this aspect. A more correct scientific use of the structure concept is to highlight the following properties. One
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can say an entity has a structure if it has two characteristics: the constituents are related in specific relationships for a sufficiently long time, compared to the phenomena considered, and these relationships affect the constituents, making specific this aggregation and transforming it in a system. An important point cannot be explored in this paper and will be investigated in future: is the modification of the components of the system strictly related to the existence of the structures of these parts? Once the structure concept is defined in this way, we can certainly say that a set of billiard balls has no structure and a molecule has. This can be reconnected to the difficulty, already noted, of the classical atomism to conceive the structure concept and explain then the emergence of new properties in the molecule (and chemical compound), compared to the aggregates of constituents. The lack of the structure concept has always rendered the atomic aggregation purely mechanical and not able to explain the new emerging, when the molecule is formed. From the scientific point of view, it is clear today that the atoms within a molecule are specifics: they are not identical to the free atoms and one talks about ‘‘atoms in situ’’. Schummer says: ‘‘today’s atoms are no atoms in the original sense, that their electronic structures and sometimes even their nuclear states, change in the course of a chemical reaction’’ (Schummer 2004). Let us consider, for example, four molecules with hydrogen atoms: H2O, CH4, C2H5OH, C6H6. All chemists know that the hydrogen atoms of the water molecule are different (they are more acidic, for example) than the hydrogen of methane, there are two different types of hydrogen atoms in the ethyl alcohol and both are different from those of the water, of the methane and of the benzene. Obviously, if we indicate these atoms with the same symbol (H), these atoms must also have something similar, but not identical. I would like to mention a last point about the concept of molecular structure and of structure in general. It makes sense to talk about the structure of a system when this is able to oppose to its variation, due to a small external perturbation. In fact, if each small perturbation will change the system structure, the system itself is at mercy of chance. It is well known that the living systems oppose resistance to the small environmental changes. Here, we would like to highlight the ‘‘stability’’ of the molecular structure. Quantum mechanics has, in fact, unwittingly provided a powerful weapon to the atomic and molecular structure and a convincing explanation of why each compound (and molecule) possesses its specific chemical properties, independently from the synthetic condition. The energy discontinuity in microscopic level justifies, in fact, this essential property (Villani 2001, Chap. 6). We close this discussion by looking at the standard definition of the molecular structure. The definition of molecular structure in terms of constitution, configuration and conformation can be fine if, defined constitution as the bond sequence, one puts then in evidence the changes of the constituent atoms generated by these bonds. It is this change, due to the specific and unique interactions among the atoms, which forms the molecular system, which creates a unique new entity. In this sense, as we have seen, one can say that a group of billiard balls, arranged in specific way on a table, has not a structure, since the balls are identical to the free balls. In this sense, the molecular structure concept can be considered a recent concept, and hence, both the classical atomists and the early modern atomists did not possess such concept. Instead, in general sense, as we have already said, the importance of parts and their qualities in the whole was understood by Aristotle and was fundamental in medieval philosophers that followed him. In conclusion, we can see that Chemistry was born in the reductionist perspective. The research, in fact, of the composition of a complex piece of matter is always a ‘‘reduction’’
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of its complexity and it is no coincidence that the analytical aspects were predominant in ancient chemistry. It is only with the ‘‘discovery’’ of the concept of molecular structure, in fact, that synthetic chemistry, today the predominant part of chemistry, has been able to develop. This story still has correspondence with the actual methodologies and the general approaches underlying. To simplify, we could say that the analytic-reductionist approach is expressed in the search of the constituents and the synthetic-holistic approach in the production of new substances. Systems in biology Having dealt in previous paragraphs the inanimate material systems, now we spend few words on living systems. Living organisms, like molecules and more, are different from physical systems and, therefore, there has always been a part of philosophy that differentiated them. The relationship part-whole is extremely complex in living systems. In Koestler’s words (Koestler 1971, p. 317), there are neither parts nor whole in absolute sense in life field and, also to the inexpert eye of philosophical questions soon becomes clear that an essential characteristic of living is to avoid decomposition. An organism is alive only as long as is ‘‘one piece’’, each substantial division ‘‘kills’’ the organism. As already said, one purpose of this paper is to highlight the conceptual (and not just practical) impossibility of the reductionism, and therefore reduction of biology to chemistry, of chemistry to physics and so on. However, equally important for this paper is to avoid inanimate-animate dichotomy and two distinct reductionisms for these two areas. In removal of the inanimate-animate dichotomy, a key role is played by chemistry. Its autonomy, its irreducibility, multiplies and dissolves the differences. The idea of this paper is as follows: the structured and/or organized entities, systems in our meaning, are present in many scientific areas and therefore do not create dichotomies, but epistemological differences. The molecule, as we have seen, is paradigmatic in this point of view. Now, we do not want to show in detail the importance of system concept in biology since is too much obvious. Here, we will deal exclusively with two specific problems: the possibility of informational reductionism in biology and the ecological relationship between the living system and its environment. Before doing so, however, a clarification should be made about the relationship between the concept of molecule (chemical system) and biological systems. The massive use of molecular explanation in biology has long supported the idea that such way of explanation could lead to the reduction of biology to chemistry. Although we claimed the importance of molecular explanation in biology, we do not think that biology can be reduced to chemistry from this concept and we think as Mayr that (Mayr 1988)5 : I concetti essenziali della genetica, come quelli di gene, genotipo, mutazione, diploidia, eterozigosi, segregazione, ricombinazione e cosı` via, non sono affatto concetti chimici e si cercherebbero invano in un manuale di chimica. Il riduzionismo teoretico e` errato perche´ confonde i processi con i concetti.
5
(my translation) ‘‘The essential concepts of genetics, such as gene, genotype, mutation, diploidy, heterozygous, segregation, recombination and so on, are not chemical concepts and one seeks in vain in a manual of chemistry. The theoretical reductionism is wrong because it confuses the processes with the concepts’’.
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For some authors, there is a new reductionist form in biology, not physicalist and mechanistic, not chemical, but informational, due to the DNA decoding. Monod, after defining living beings as ‘‘chemical machines’’, adds (Monod 1997, pp. 45–46)6 : Come ogni macchina, ogni organismo, anche il piu` semplice, rappresenta un’unita` funzionale coerente e integrata. E` ovvio che la coerenza funzionale di una macchina chimica tanto complessa, e per di piu` autonoma, esige l’intervento di un sistema cibernetico che controlli in piu` punti la sua attivita`. Even if enzymes play to perfection their tasks in each reaction, the cellular metabolism will inevitably end up in chaos if these reactions are not subordinated to each other. The informational aspects can be incorporated in both points of view: the reductionist and holistic. In fact, the molecular genetics is a sui generis form of reduction (not more physical-chemistry, but based on the science of communication). More than reductionism in classical sense, in modern biology one must speak of ‘metaphorical loan’, which does not leave unchanged the language of communication theory: code, translation, error of copying, etc. are all theoretical terms constitutive of genetic dictionary, which apply to the interpretation and explanation of the DNA meaning, but work differently of corresponding terms of science of communication. To grasp the meaning and scope of the DNA decoding of Watson and Crick, one must not forget what happened in the same years in the science of communication (with elaboration of ‘information’ concept by Shannon and Weaver), but one must also see how these concepts, exported in genetics, were modified. In the fifties and sixties of the twentieth century, the overcoming in the molecular biology of the explanatory reductionism was achieved with the use of explanations of Information Theory applied to the genetic code, but in recent years the focus is once again moving in the direction of the structural aspects of the genome. It is, in fact, found that the DNA has its own conformation, sedimented in time and that depends on its environmental conditions, which can be explored with chemical-physics methods. We can thus see a reversal. The day after the decoding of the genetic code, each structural research on DNA has been considered an expression of old-physicalist reductionism. The informational approach, instead, revolutionized the ability to study the live and highlighted the autonomy of biology from the exact sciences. The rediscovery of the structural aspects now also exists as a bulwark to the excess of informational reductionism. We would like to close this section with the Morin position on open-closed living systems, position shared by us. The environment concept must become that of eco-system, a natural unit formed from the living things of a ‘niche’ (biocenosis), inorganic environment (biotope) and all their interactions. For each living organism, ecosystem is much more of a food reserve or a source of negative entropy from which it derives its organization, its complexity and the informations. It is one of life dimensions, no less essential than the individuality, the society and the reproduction cycle. The environment cooperates, in fact, at any time with the living organization that is, hence, in permanence ecodependent. The eco-dependency gives a dual identity: one which distinguishes and the another which connects it to its ecological environment. Morin says (Morin 2001, p. 235)7 : 6
(my translation) ‘‘Like every machine, every organism, even the most simple, represents a coherent and integrated functional unit. It is obvious that functional coherence of a so complex, and also independent, chemical machine requires intervention of a cybernetic system that controls its activity in several points’’.
7
(my translation) ‘‘Such beings can build and maintain its existence, independence, individuality, and originality, only in the ecological relationship, that is in and through the dependence from their environment. It born from this the alpha idea of every ecological thought: the independence of a living being requires the dependence from surrounding environment’’.
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Tali esseri possono costruire e mantenere la loro esistenza, la loro autonomia, la loro individualita`, la loro originalita`, solo nel rapporto ecologico, cioe` in e attraverso la dipendenza nei confronti del loro ambiente. Nasce di qui l’idea alfa di ogni pensiero ecologizzato: l’indipendenza di un essere vivente ne richiede la dipendenza nei confronti dell’ambiente che lo circonda. This opening is not a window on environment and the open organization can not be inserted as merely a part of the whole: organization and environment, while remaining distinct one from the other, are one into the other. The existence is at once immersion in its environment and separation from it. On one side, one can not give any possibility of separate and independent existence; on the other side, it takes a certain detachment, autonomy, i.e. a minimum of individuality, for existing. The opening of living system is therefore much more radical than that of thermodynamics. It is deeper than the idea of the discoverers of the ‘open system’ because these have caught only external characteristics of phenomenon (input–output, steady state and so on). They certainly have revealed importance of ecological relationship, but without drawing all consequences. Opening is a notion at once organizational, ecological, ontological, existential and, this polydimensional notion requires a complete intellectual reorganization. The role of chemical entities in the biological explanations is of two types. In fact, reduce a biological problem to molecules involved, to their reactions and interrelationships may be just a ‘‘reduction’’, hence, an approach that moves in reductionist perspective. This approach is part of a more general reductionist idea that reduces the human behavior to its biological basis, the biological process to molecules and chemical transformations, the molecules and reactions to atoms and their interactions, the latter to the constituent particles, and so on. It should be borne in mind that, in the correct reductionist perspective, this chain must be tackled all (at least in principle), arriving at the elementary particles and their interactions. If you are working with a single ring of this chain, for example that which connects biology to chemistry, the general perspective, as well as reductionist, can also be framed in the areas of the complexity and/or of the systemic. Also in these areas, in fact, no one denies that the level of complexity of cells is connected with the underlying molecular level and that, although not in an exhaustive way, the molecular explanations provide information on cellular processes. In this respect, clear and substantially acceptable, is the position of Canguilhem8 : Nessuno si sogna di disprezzare lo studio volto a determinare e misurare l’azione di questo o quel sale minerale sulla crescita dell’organismo, oppure a stabilire un bilancio energetico o inteso a cercare di realizzare la sintesi chimica di un certo 8
G. Cahguilhem, La conoscenza della vita, il Mulino, Bologna 1976, in L’epistemologia francese contemporanea, a cura di C. Vinti, Citta` Nuova Editrice, Roma 1977, p. 241. (my translation) ‘‘No one dreams of despising the study to determine and measure the action of this or of that mineral salt on the growth of the organism, or to establish an energy balance or should seek to achieve the chemical synthesis of a certain adrenal hormone or search the laws of transmission of the nervous impulse or the conditioning of reflexes. But this is not a fully biological knowledge as long as we are not aware of the meaning of the corresponding functions. The biological study of nutrition is not only to set up a balance sheet, but in looking within the same organism the meaning of the choice that it operates spontaneously in its environment when makes of certain kinds of species or of substances its food, excluding others that theoretically could give it, for its maintenance and for growth, equivalent energy inputs. […] It is a general rule for biological thought that a knowledge obtained through analysis reaches its full capacity only when it takes the form determined by reference to an organic existence grasped in its totality. […] Only the representation of the whole allows you to determine the value of the facts established and to distinguish those who really have to do with the organism from the others who are for it meaningless’’.
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ormone surrenale o a cercare le leggi della trasmissione dell’impulso nervoso o del condizionamento dei riflessi. Ma tutto questo non e` pienamente una conoscenza biologica finche´ manca la coscienza del senso delle funzioni corrispondenti. Lo studio biologico dell’alimentazione non consiste solo nel mettere in piedi un bilancio, ma nel cercare entro lo stesso organismo il senso di quella scelta che esso opera spontaneamente nel suo ambiente quando fa di certe specie o sostanze il proprio alimento, escludendone altre che teoricamente potrebbero procurargli, per il suo mantenimento e per la sua crescita, apporti energetici equivalenti. […] E` regola generale per il pensiero biologico che una conoscenza ottenuta attraverso analisi raggiunga la sua portata intera solo quando assume la forma determinata dal riferimento a un’esistenza organica colta nella sua totalita`. […] Soltanto la rappresentazione della totalita` permette di stabilire il valore dei fatti appurati e di distinguere quelli che hanno veramente a che fare con l’organismo da quegli altri che sono per esso privi di significato. In the application of chemistry to biology remains to be clarified a further point that connects back to the question: why the use of biochemistry in biology is more prevalent than that of biophysics? The explanation is implicit in the previous analysis of chemical and mechanical systems (for a more detailed analysis see Villani 2001, Chap. 11): given that chemistry is a systemic science (since compounds and molecules are systems), a discipline like biology, that moves from long time in this context, relates better with chemistry than with physics, where the system concept (entity structured and/or organized) is rarely or completely not applicable. All this raises the question of the relationship between the chemical and the biological explanations and the physical one. The problematic nature of the specific biological laws (and chemical) appears to many biologists as a deficiency, as something to be removed using the physical example. To us, however, seems to be a normal consequence of the field of study of biology: the collective entities, such as the species, and the individual ones, such as the specific beings, can not dissolve completely in the universality of the laws, as in the case of physics but not of chemistry, and, therefore, in biology and chemistry is more the general that you can draw than the universal. It is in this way that biology and chemistry can scientifically master the matter, including that differentiated qualitatively and the living (Villani 2008, Chap. 3). In particular, a matter broken down into specific entities, to which they are assigned names and their individual characteristics, a matter populated by millions of those entities, be they chemical species or biological ones. Moreover, the differences in quality can not be dissolved completely in the universal/general and, in addition to these concepts, remains always the particular, the individual. In fact, everything in living world, also the entity that seems more stable and unchanged, is the product of a more or less distant past and its historical ties, linear and cumulative or due to massive discontinuities. A link between the past and the future that can be found in the entities and in the processes of the planet and in the organisms.
Conclusion Until now, we have underlined the importance of system concept in science. Nevertheless, this is so well hidden in physics and chemistry that this concept seems the base of the inanimate-animate dichotomy: living systems as opposed to physical and chemical unstructured entities. The indivisibility of the firsts opposed to the decomposability of the
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seconds. If one then moves to human sciences, to the social and anthropological disciplines, one sees again the increase of importance of this concept until to arrive to individuality of each human living system, the individual person. In this paper we have tried to show that the system concept, also with different importance, plays an essential role in both inanimate and animate natural sciences, as well as in the human ones. It may therefore be a unifying concept and the General System Theory, despite its limitations, can be a good example. A central role in system concept is played by chemistry, as mentioned, since this discipline is the first true systemic science (Villani 2010). Two examples can clarify this role: the Alchemy project of Fontana and Buss and the molecularism in philosophy of language. Following the words of Walter Fontana and Leo W. Buss, the dynamical systems view formally separates the entities and the interactions in which they engage. To go beyond this framework requires removing that separation. The goal of the Alchemy project is to develop a theory of biological organization by adding a constructive component to dynamical systems. A theory of biological organization must be grounded in a representation of that which organisms are composed. The theory must be grounded in chemistry, the real-world entities of interest in this project are molecules. Otherwise, mental (or semantic) holism in the philosophy of language is the doctrine that the identity of a belief content (or the meaning of a sentence that expresses it) is determined by its place in the web of beliefs or sentences comprising a whole theory or group of theories. It can be contrasted with two other views: atomism and molecularism. Molecularism characterizes meaning and content in terms of relatively small parts of the web in a way that allows many different theories to share those parts. Atomism characterizes meaning and content in terms of none of the web; it says that sentences and beliefs have meaning or content independently of their relations to other sentences or beliefs. In mechanistic-reductionist thought, as seen, each system is considered free, with no significant interrelationship with other systems or subsystems or environment and only linear causes work between theirs, with unidirectional relationship between cause and effect. The world of systemic paradigm, instead, is radically different, richer, characterized from a dense weave of relationships. Of course, one needs to navigate in these interrelationships, set benchmarks and identify key issues. Even in these aspects, the difference with the mechanistic point of view is radical: the key concept of this last can be found in the causes (past) which generate a certain state/phenomenon, hence, taking a diachronic perspective that considers the present as a result of the past. The systemic approach, by contrast, tends to give greater importance to the current factors which contribute to maintain this particular state/phenomenon, rather than those which generate it. Its perspective is centered on the present and, therefore, is synchronous and its processes do not break in phases and distinct roles, but are considered in their entirety and circularity. This means to place all objects in study on same level and try to understand how each contributes to persistence of a certain state of fact: to characterize homeostatic functions (from Greek Ho`moios = similar and sta`sis = to stay, therefore: do not change, remain the same). In the systemic approach one of keystones is the identification of the homeostatic processes rather than of the initial generator factors. In fact, the steady state of the open system is to some extent independent of its initial state, and is mainly determined by the process nature and by the system parameters. Homeostatic processes of this system, are often present also in systems of other levels (supra- and sub-systems) in relation with it. Each system has in fact not only internal homeostat, but is inserted in a homeostatic environment which limiting the possibility of the oscillations of its states. A few last words must be spend on the relationship between the system concept and its time dependence. We have not considered in detail this fundamental aspect in this paper,
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but the importance of the time transformation in chemistry is in any case well present in this paper. In fact, it is impossible to eliminate the time from chemistry that is not only but also ‘‘the science of the transformation of substances’’ (van Brakel 1997). We will consider explicitly the relationship between the system concept and its time transformation in a following paper.
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