Hume on simple perceptions

Hume on simple perceptions in E. Mazza and E. Ronchetti (eds), New Essays on David Hume Milan: Franco Angeli, 2007 Marina Frasca-Spada Abstract This paper is devoted to the notion of ‘simple perceptions’ as presented by Hume in the Treatise of Human Nature. That notion is at the very core of Hume’s science of human understanding, as well as being ambiguous and difficult to reconstruct in a coherent way. I consider in turn the spatial simplicity of the coloured points that according to Hume compose visual extension, then the simplicity derived from selective attention in his discussion of the so-called distinction of reason. These two accounts suggest different interpretations of Humean simple perceptions. My conclusion is that the second makes better sense of the various appearances of simplicity in the Treatise, and show how it does, in fact, also involve a key element of the first. Keywords: simple and complex impressions; simple and complex ideas; indivisible points; minima sensibilia; distinction of reason; resemblance; science of human nature §1 — Introduction The distinction between simple and complex perceptions appears in the first section of the Treatise, just after the better-known one between the more and the less immediate and compelling among our perceptions, impressions and ideas: There is another division of our perceptions, which it will be convenient to observe, and which extends itself both to our impressions and ideas. This division is into SIMPLE and COMPLEX. Simple perceptions or impressions and ideas are such as admit of no distinction nor separation. The complex are the contrary to these, and may be distinguished into parts. Tho’ a particular colour, taste, and smell, are qualities all united together in this apple, ’tis easy to perceive they are not the same, but are at least distinguishable from each other. (T2) Hume’s attention in this passage seems focussed on the complex, rather than on the simple perceptions; even though the exposition of the example starts with a list of qualities, its emphasis is on the obvious complexity of the apple. As we shall see, this focus on the complex rather than on the simple perceptions is somewhat typical. In any case, here we have an explicit definition: simple ideas admit of no distinction or separation, while complex ideas are ‘the contrary’ of simple ones and are distinguishable into parts. Things seem clear enough, especially thanks to the example. The perception of an apple is complex because the perceptions of its colour, taste and smell which by their union compose that perception can be distinguished from each other, that is, considered separately. And it seems to be suggested, even though it is not openly stated, that those perceptions of colour, taste and smell are simple (perhaps on account of their belonging each to just one sensory modality).

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With ‘simple ideas’ or ‘simple perceptions’ thus defined, Hume’s theory is, to all appearances, in line with a traditional part of the so-called classical empiricist views of human perception and mind, according to which: 1) Simple ideas are the components of compound or complex ideas. While in actual experience they present themselves clustered in complex ideas, they are easily distinguishable from each other; conversely, after separating them the mind can mix, combine and rearrange them to produce a variety of new complex ideas. 2) Differently from complex ones, simple perceptions are not, and normally cannot be, thus constructed by the mind. Standard examples of simplicity, as given, for instance, in Locke’s Essay, variously include specific sensational contents such as the softness and warmth of a piece of wax, the whiteness and smell of a lily, the smell of a rose, the hardness and coldness of ice, the taste of sugar, and so on, as well as ideas of qualities such as extension, figure, rest and motion, number, and also pleasure and pain, power, existence and unity.1 We shall see how, as well as the apple, Hume mentions various colours, the taste of a pineapple, the colour, taste and other features of several other fruit, etc. Hume is notorious for presenting in a deceptively easy manner doctrines that a closer look often reveals as highly controversial and counterintuitive.2 This is the case, it may be maintained, even with the distinction between impressions and ideas.3 Here in the case of simple and complex ideas Hume’s smooth prose seems to do exactly the opposite, to expose the potential for trouble contained in the traditional notion of simplicity. There is a host of difficulties with that doctrine. Consider again Locke’s way of illustrating his notion of simple ideas—what do extension or duration have in common with the smell of a lily? And in what sense are length and breadth (or indeed extension and duration) supposed to be simple?4 As we shall see, within Hume’s frame of reference these difficulties become more dramatic. The aim of this article is not primarily to offer an unambiguous answer about the nature of Hume’s simple perceptions, but to raise questions about them. In fact, ultimately I intend to show how it is impossible to tidy them up in order to restore full consistency and analytic viability: Hume’s whole treatment of the notion of simplicity is not only far from 1

See Locke, Essay concerning Human Understanding (II, 2, 1; II, 8, 2–3; II, 5 and II, 8, 9; II, 7, 1). 2

See J. J. Richetti, Philosophical Writing: Locke, Berkeley, Hume, Cambridge (Mass.): Harvard University Press, 1983, ch. 4 ‘Hume’, esp. pp. 85 ff. 3

See my ‘Hume on sense impressions and objects’, in M. Heidelberger and D. Stadler (eds), History of Philosophy of Science. New Trends and Perspectives, Vienna Circle Institute Yearbook 9/2001 (Kluwer Academic Publishers, 2002), 13–24. 4

For a discussion of the simple/complex distinction in Locke’s Essay and a comparison with the former tradition and Descartes see M. Ayers, Locke, London: Routledge, 1991, Volume 1: Epistemology, ch. 2, ‘Ideas and compositionalism in traditional logic’, pp. 19–25, and ch. 4, ‘Simple and complex ideas’, pp. 36–43. Interesting, if brief remarks also in W. Waxman, Hume’s Theory of Consciousness, Cambridge: Cambridge University Press, 1994, pp. 42–44 and relative footnotes. 2

straightforward, but also rather messy. This mess is an interesting one, however, being caused by his typically unsystematic, but repeated and deep probing of new issues concerning human knowledge. I start, in section 2, by considering the way Hume introduces the notion of ‘simple perception’. While doing so, I highlight both the importance of this notion for the Humean ‘science of the human mind’, and Hume’s apparent lack of interest in the nature of simple perceptions themselves. In sections 3 and 4 I try to clarify the picture by following Hume’s own well-known advice, whenever there is trouble with ideas, to explore the corresponding impressions: what does Hume think is a simple impression? In this connection I show how, contrary to what one would reasonably expect, the spatial simplicity of visual minima does not make them particularly good representatives of Humean simple impressions in general. In fact, in the Treatise there is a whole range of senses, not all compatible with each other, in which an impression (or an idea) may be called ‘simple’, from the spatial simplicity of visible points to various forms of temporal simplicity and immediacy of apprehension. I then consider, in section 5, Hume’s account of the patterns of resemblance we can identify among simple perceptions. This part of Hume’s discussion seems to suggest a very different interpretation of the simplicity of perceptions: just like the resemblance among simple perceptions, so their very simplicity too belongs together with our reflected responses and passions. This would account for the elusive nature of that simplicity. I conclude outlining the advantages of this second interpretation and suggesting that it is in line with Hume’s way of treating the indivisibles of perception. §2 — Complex (and simple) ideas The conjunction of the distinction between simple and complex with that between impressions and ideas is at the foundation of Hume’s analysis of perception, being used to formulate his all-important ‘general maxim’ that all our ideas are preceded by corresponding impressions, of which they are faithful, if paler, copies. In fact, the principle establishes that correspondence only between simple impressions and simple ideas: every simple idea has a simple impression, which resembles it, and every simple impression a correspondent idea. That idea of red, which we form in the dark, and that impression which strikes our eyes in sun-shine, differ only in degree, not in nature. (T3) To be entirely accurate, this statement of Hume’s general maxim follows a series of remarks to the effect that complex ideas are indeed copied from impressions—but often they are not, in fact, copies of impressions, that is, they are not exactly paired with their corresponding impressions. As Hume puts it: I observe, that many of our complex ideas never had impressions, that corresponded to them, and that many of our complex impressions never are exactly copied in ideas. I can imagine to myself such a city as the New Jerusalem, whose pavement is gold and walls are rubies, tho’ I never saw any such. I have seen Paris; but shall I affirm I can form such an idea of that city, as will perfectly represent all its streets and houses in their real and just proportions? I perceive, therefore, that tho’ there is in general a

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great resemblance betwixt our complex impressions and ideas, yet the rule is not universally true, that they are exact copies of each other (T3). Hume is here indicating that there is an odd imperfection of fit between the collection of our actual past impressions of Paris and the collection of impressions from which the idea of Paris is, in actual fact, derived. In other words the remembered idea of Paris, even though it is supposed to derive from experience directly, is just as much of a patchwork of disparately acquired ideas as the imaginary idea of the New Jerusalem. If ultimately all our ideas derive from former impressions, this is because complex ideas consist of combinations of simpler ones, however acquired. In a similar vein Hume refers to the simple/complex distinction when describing the freedom with which our imagination can ‘transpose and change its ideas’: for ‘wherever the imagination perceives a difference among ideas, it can easily produce a separation’. This phenomenon ‘is an evident consequence of the division of our ideas into simple and complex’, he emphasises. As examples of it he mentions the ‘winged horses, fiery dragons, and monstrous giants’ of poems and romances (T10), and, later on, the idea of a golden mountain (T32). Of course the idea of a golden mountain is put together by the imagination from the ideas, acquired separately by being extracted from different complex ideas, of mountain and of gold; a winged horse, from those of wings and of horses, and so on. In these passages Hume is certainly not implying that the ideas of mountain and gold, wings and horses, etc. are themselves simple. In fact, while deconstructing the idea of substance as ‘nothing but a collection of simple ideas, that are united in the imagination, and have a particular name assigned to them’, he gets back to the idea of gold again as an example of a substance, and explicitly says that it is itself complex, being composed of such ideas as ‘yellow colour, weight, malleableness, fusibility […] dissolubility in aqua regia’ (T16). In turn, the component ideas in this list cannot all be taken as simple. Since colours are Hume’s favoured example of simplicity, for argument’s sake we can take the yellow colour of gold to be simple; and perhaps weight may be regarded as simple too. But malleability, fusibility, and, even worse, solubility in aqua regia evidently include elements which can be conceived separately, and thus are definitely rather awkward. So, just as the idea of gold is complex, so must be, in some sense, the ideas of some of its qualities, as more obviously are the ideas of pavement, walls, rubies, mountain etc., even though each of them may play, on particular occasions, the part of the components of more complex ideas. All or most of our complex ideas can presumably play such a part in some situation or other. In sum, it appears that simple perceptions are at once crucially important—insofar as they provide the foundation of Hume’s theory of perception and key elements for its concrete workings—and rather difficult to pin down. Simple perceptions admit of no distinction or separation, and the impression and idea of red are explicitly called simple; but this is as far as Hume goes in explaining himself on this matter. He is subtle and careful in explicating and illustrating in detail the (sometimes unobvious) ways in which complex ideas can be both put together by the mind, and split into simpler components (some of them, perhaps, actually simple) which can in turn be combined again to compose different complex ideas. By contrast, he seems to be positively absent-minded and vague when it comes to discussing or expanding on the simplicity of simple perceptions.

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§3 — Simple impressions of coloured points We have seen that Hume reproduces, within the simple/complex distinction, his own newly introduced distinction between impressions and ideas; and how in his text the emphasis is still all on the side of complex ideas. This is perhaps a trace of the Lockean approach. Nevertheless, Hume’s simple ideas must be quite different from Locke’s in that the key to their nature is to be found not in the nature of the corresponding objects but rather—as always with ideas, if we are to trust Hume—with the corresponding simple impressions. So it is worth trying to follow Hume’s own method by looking at the impressions, where, hopefully, all will be clearer. Now the question is: what are Hume’s simple impressions? In Book 1 of the Treatise there are apparent obvious candidates for the position of ‘simple impressions’: the coloured points which Hume invokes in the course of his notorious rejection of the ‘doctrine of the infinite divisibility’ in Part 2. We simply cannot conceive space or extension as infinitely divisible, Hume maintains here, since, whenever we embark on a process of successive divisions of and subdivisions, our perception invariably ends up rather soon presenting us with indivisible points. Moreover, it can be shown that such perceptual indivisibles are available individually to our very eyes: Put a spot of ink upon paper, fix your eye upon that spot, and retire to such a distance, that, at last you lose sight of it; ’tis plain, that the moment before it vanish'd the image or impression was perfectly indivisible (T27). These indivisible points are, Hume maintains, essential components of our sense perception of space or extension. On the level of ideas we also are presented with indivisibles—for it is obvious that ‘the idea of a grain of sand is not distinguishable, nor separable into twenty, much less into a thousand, ten thousand, or an infinite number of different ideas’ (T27). Accordingly, this is how he describes the origin of our idea of space: The table before me is alone sufficient by its view to give me the idea of extension. This idea, then, is borrow’d from, and represents some impression, which this moment appears to the senses. But my senses convey to me only the impressions of colour’d points, dispos’d in a certain manner (T34). Having identified the visual indivisibles thanks to the spot of ink, Hume finds it easy now to trace them again, thanks to their colour, among the objects of his common experience (in this case, famously, the points composing the surface of his table are purple).5 There is no doubt that these ‘simple indivisible points’, as Hume calls them a few pages later (T38), provide a very tempting possible answer to the question of how to identify Humean simple impressions. Accordingly, recent Hume readers have often generalized them by renaming them minima sensibilia or ‘perceptual atoms’, and regarded them as one and the same

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See J. Franklin, ‘Achievements and fallacies in Hume's account of infinite divisibility’, Hume Studies 20, 1994, 85–101, for a count of the Humean minima, i.e. pixels, composing our visual field. 5

as ‘simple perceptions’.6 This interpretation is natural and has its obvious merits. In particular, by pinning simplicity down to spatial minima we would satisfactorily tidy up a rather confused and confusing part of Hume’s theory of the understanding. Moreover, Hume openly and repeatedly calls the points ‘simple’, and here and there contrasts the ‘simple and indivisible points’ with extension itself, which ‘consists of parts’ (e.g. T38)—so, for what it is worth, this reading does command a certain amount of literal textual support. It also faces serious problems, however. 1) For starters, interpreting simple impressions as ‘indivisibles’ or minima sensibilia without further ado would not make good sense of what Hume writes elsewhere in Book 1 of the Treatise about simple perceptions and ideas. For instance, this reading would not sit easily with Hume’s choice of the impression and remembered idea of red as examples of simple perceptions, which would be rather strange if what he had in mind was an indivisible red point (T3). That is by no means an isolated case. Other passages at odds with this interpretation include the following remarks on memory and the imagination: The chief exercise of the memory is not to preserve the simple ideas, but their order and position (T9). … all simple ideas may be separated by the imagination, and may be united again in what form it pleases… (T10). It is difficult to imagine that in such passages Hume intended to refer to ideas of minima sensibilia. He does not seem to mean that memory preserves the exact order of the purple points composing the surface of his table, while the imagination is free to transpose them at will, etc.7 Admittedly, Hume must be using ‘simple’, in such passages as the two just cited, in the relative sense in which ‘wings’ and ‘horse’ are ‘simple’ vis-à-vis the idea of a winged horse. But then, it is rather odd that he does not make any distinction between the relative sense and the apparently absolute sense which is supposed to be applicable to the simplicity of visual indivisibles. But this is not all; for there are also internal problems with the identification of simple impressions and visual minima. 2) Simple impressions are presented as objects of relatively easy and unproblematic apprehension—the colour, smell and taste of the apple, or the impression and idea of red, seem to be immediately given and available as objects of our common experience, without much analytic manipulation (T3). In spite of Hume’s rhetoric, the visual minima are not. Consider again the case of the spot of ink. The first-approximation description cited above 6

See for example D. Garrett, Cognition and Commitment in Hume’s Philosophy, New York and Oxford: Oxford University Press, 1997, pp. 60–62 (who uses both ‘perceptual atoms’ and ‘minima sensibilia’); and, with some sound reservations, Waxman, pp. 44–46. 7

See Daniel Schmicking, ‘Hume’s Theory of Simple Perceptions Reconsidered’, Hume Studies 30, 2004, 3–32. 6

does the job very well, making it very ‘plain’, as Hume puts it, what he has in mind when he talks about indivisible points being available to our very senses. But in fact, Hume is well aware that in practice things are not quite so straightforward, and some pages later comes up with a more subtle—and for our purposes less conclusive—account of the spot of ink experiment: Put a spot of ink upon paper, and retire to such a distance, that the spot becomes altogether invisible; you will find, that upon your return and nearer approach the spot first becomes visible by short intervals; and afterwards becomes always visible; and afterwards acquires only a new force in its colouring without augmenting its bulk; and afterwards, when it has encreas'd to such a degree as to be really extended, 'tis still difficult for the imagination to break it into its component parts, because of the uneasiness it finds in the conception of such a minute object as a single point (T42). In other words, when regarded in closer detail Hume’s little experiment with the spot of ink singles out an event rather than the unambiguous spatial unit he was after. For where are we to pin down the minimum sensibile? Is it the spot that is still flickering, or the one that has just stabilised, or the one whose colour has reached it full ‘force’, or even the one that is ‘really extended’ but in practice not quite divisible yet? So in principle surely coloured points may well be visual units and perceptual indivisibles—in practice, however, they turn out to be very slippery objects indeed. This seems to makes them somewhat less satisfactory in the role of simple impressions. 3) Moreover, the ‘composition’ of purple points forming the surface of Hume’s table is found to resemble other compositions of points of different colours, and indeed the impressions of sight are ‘found to be similar’, in ‘disposition’ or ‘manner of appearance’ to those of touch as well. The process that identifies this pattern of similarities results in the abstract idea of space; and thereafter the indivisible points composing space are simply called ‘coloured and tangible’ (T34). It is, I believe, well known that Hume’s coloured and tangible points are rather paradoxical items in their own right for various reasons. For example, they are nonphysical and non-extended, and (crucially for us in the present connection) Hume attributes to them ‘the perfect simplicity, which excludes all parts’ which is typical of mathematical points (T40); and yet, he also says that they compose extension (T38). Hume’s answer to the obvious conceptual problems thus opened is difficult to interpret and not fully satisfactory: his points are, he says, neither mathematical, nor physical, but specifically perceptual; as such, we can only conceive of them as coloured and tangible; and he insists that, as soon as we remember their colour and solidity, all becomes perfectly clear (see e.g. T40–42). Thus identified, these perceptual minima are so problematic, that even Hume in the end gave up on them: when he got round to simplifying his system into a more readable form, in the Enquiry, he identified them with physical points without further ado.8 But perhaps this is not essential to our current concerns; and it is true that the perceptual points giving rise to the idea of space are at least, by definition, (spatially) indivisible, and in this sense simple—Hume’s own words are worth repeating once more: their ‘perfect simplicity […] excludes all parts’ (T40). 8

For a fuller analysis of the difficulties of the coloured and tangible points as presented in the Treatise see my Space and the Self in Hume’s ‘Treatise’, Cambridge: Cambridge University Press, 2000, ch. 1 ‘Reality and the coloured points’, passim. 7

What we cannot so easily ignore, however, is that they are ‘impressions of atoms or corpuscles endow’d with colour and solidity’ (T38). In other words, for all their spatial simplicity, in each of them we can ‘distinguish’ two different aspects, colour and tangibility (T41, T34), and in this sense they are, strictly speaking, not much better, as examples of simple impressions, than the very apple presented earlier as the example of a complex perception. Spatial indivisibility is not enough for simplicity: the coloured and tangible points are spatially simple, but in at least one specific sense they are complex nevertheless. 4) So far I have not questioned that visual points could be good illustrations or representatives of perceptual units. But is this really so? Can vision provide a satisfactory general representation for simple impressions belonging to other sensory modalities, or do those exhibit different kinds of simplicity? It is perhaps too easy to suggest that a purple point from Hume’s desk may not be a good image for the taste or scent of his apple. But even if we limit ourselves to consideration of spatial impressions we find important discrepancies between the simplicity of visual and tactile sensations. For it is true that, as we have seen, on several occasions Hume talks of ‘colour’d and tangible points’. What is not clear is whether he thinks of tangible points as tactile units in the same sense in which visual points are visual units, that is, if he regards them too as ‘simple’: are they too exhibited in common perception, in a tactile equivalent of the spot of ink experiment? And what exactly is a tactile unit supposed to feel like to our touch—if it is to be in a one-to-one correspondence with a visual unit, it would be perhaps like a pin-prick on the tip of one’s finger? But in fact, in other parts of the Treatise Hume seems to be clear that the simplicity of tactile impressions has nothing to do with spatial indivisibility. As he puts it: … the impressions of touch are simple impressions, except when consider’d with regard to their extension; which makes nothing to the present purpose (T230–231).9 So as well as spatially simple impressions which can in other respects be complex (the socalled minima sensibilia), we are now presented with spatially complex impressions that are in all other respects simple. Hume’s use of the language of simplicity is not easy to follow, in fact it seems not to be completely consistent. And yet, what he seems to have in mind here when he talks of the simplicity of tactile impression follows exactly from his original definition of simplicity. The example following the statement above talks of ‘a man, who presses a stone, or any solid body, with his hand’, and compares it to the case ‘of two stones, which press each other’. The difference between these two cases is, he says, all in the feeling or sensation appearing in the former, and it cannot be eliminated: for that feeling cannot be removed without removing the whole perception, ‘that being impossible in a simple impression’ (T231). So the simplicity of this kind of tactile impression has to do specifically with the impossibility of distinguishing and separating aspects (i.e. non-spatial ‘parts’) within it. This epistemic and phenomenological simplicity cannot easily be represented by a visual minimum. The situation is the same in the case of other impressions too—passions, which in Book 2 of the Treatise are also, just like visual points, repeatedly called simple: 9

This passage comes from Hume’s sceptical attack against the primacy of primary qualities in Part 4, his main argument being that we certainly should not regard touch, with its simple impressions, as providing a representation of solidity, since in his view solidity presupposes a compound object. 8

The passions of PRIDE and HUMILITY being simple and uniform impressions, ’tis impossible we can ever, by a multitude of words, give a just definition of them, or indeed of any of the passions (T277). ’Tis altogether impossible to give any definition of the passions of love and hatred; and that because they produce merely a simple impression, without any mixture or composition (T329). Their attending circumstances or their histories may vary; but the passions themselves are ‘simple and uniform’, and as such they cannot be defined, presumably because they do not appear to have distinguishable and separable aspects. 5) Finally, anyone familiar with Book 1, Part 2 of the Treatise knows how the whole discussion is based on the parallels and similarities between space and time. But then, we should expect Hume’s theory also to allow, alongside the spatial minima, for simple time perceptions, or, as Hume calls them, ‘indivisible moments of time’ (T39). While the idea of space arises by the mere sight of an arrangement of visual indivisibles such as the purple points, the idea of time arises from hearing five notes played on a flute (T36). The simplicity of each note is, of course, problematic in various ways—in that it is difficult to think of a note, however brief, which is itself devoid of any temporal duration. Hume does not spend much time on this kind of problem with temporal indivisibles; he simply states that ‘each moment, as it succeeds another’ must be ‘perfectly single and indivisible’ if we are to avoid falling into the ‘arrant contradiction’ of supposing ‘an infinite number of co-existent moments, or parts of time’ (T31). In this respect, the situation of the indivisible moments is similar to that of the coloured points, which are at best intermediate between extended and non-extended: temporal indivisibles must be an intermediate between duration and nonduration. We can only make hypotheses on what else, aside from the five notes, can count as an indivisible moment: perhaps, among the visual impressions, snapshots of our visual field or objects apprehended at a glance, instantly, and in that sense indivisible. These temporal minima would be ‘des points d’affet’, as A. Michaud has called them.10 As such, their simplicity may be closer to the simplicity of non-visual impressions, or indeed of passions. We can now take stock and try to produce a map of the various forms in which Hume’s notion of simplicity is embodied at the level of impressions. There are: 1) The simplicity which, in the case of the apple, Hume seems, admittedly rather absentmindedly, to attribute to the sense impressions of its colour, smell and taste. 2) The simplicity of the coloured and tangible points, which coincides with spatial indivisibility and coexists with a high degree of epistemic complication and the presence of colour and solidity, which are as distinguishable from each other as the colour, smell and taste of the apple. 3) There is then the epistemic simplicity of (spatially complex) tactile impressions. 4) Then, there is the simplicity of passions. 5) Finally, there is the simplicity of temporal indivisible moments. 10

A. Michaud, ‘Remarques sur l’atomisme et le phénoménalisme de Hume’, Les Etudes Philosophiques 46, 1973, 43–57. 9

These forms of simplicity correspond to different criteria—mereological, predicative and emotional—that are not compatible with each other in the specific sense that, if applied to the same things, they will often give different answers. Examining impressions certainly has enriched the picture, but quite as certainly it has not clarified it. In this sense, the case of simple perceptions seems to be at odds with Hume’s stated view that what is obscure and confusing in ideas is usually illuminated by examination of the corresponding impressions. Simple impressions seem to be just as problematic as simple ideas. This is not all: they are also just as difficult to identify. As Hume himself puts it in discussing the origin of the ‘ancient’ philosophical idea of substance: Suppose an object perfectly simple and indivisible to be presented, along with another object, whose co-existent parts are connected together by a strong relation, ’tis evident the actions of the mind, in considering these two objects, are not very different. The imagination conceives the simple object at once, with facility, by a single effort of thought, without change or variation. The connexion of parts in the compound object has almost the same effect, and so unites the object within itself, that the fancy feels not the transition in passing from one part to another. Hence the colour, taste, figure, solidity, and other qualities, combin’d in a peach or melon, are conceiv’d to form one thing; and that on account of their close relation, which makes them affect the thought in the same manner, as if perfectly uncompounded. But the mind rests not here. Whenever it views the object in another light, it finds that all these qualities are different, and distinguishable, and separable from each other; which view of things being destructive of its primary and more natural notions, obliges the imagination to feign an unknown something, or original substance and matter, as a principle of union or cohesion among these qualities, and as what may give the compound object a title to be call’d one thing, notwithstanding its diversity and composition. (T221)11 At this stage it probably does not come as a surprise that, yet again, in comparing the actually simple and the apparently simple objects, Hume is so vocal on the variety of aspects composing a peach or a melon, but is entirely silent on the nature of that other object, the ‘perfectly simple and indivisible’ one. Like the apple, here the peach and the melon are complex perceptions; and there is no more than the suggestion, never made explicit, that their colour, taste, figure, solidity and other qualities which combine to form them are themselves simple. What is, perhaps, a bit more surprising is that the case of simple perceptions seem to subvert his view of the relation between impressions and the corresponding ideas. So at least in the case of simplicity and complexity, the idea seems no less clear, indeed possibly is less deceitful than the impressions. §4 — A globe and a cube of white marble, and a tasty red apple

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For a still fascinating discussion see H. H. Price, Hume’s Theory of the External World, Oxford: Clarendon Press, 1940, ch. 2, ‘Constancy and coherence’, pp. 11–36. 10

So far my discussion has followed the usual approach and focussed on the fact that simple perceptions are not supposed to be distinguishable into ‘parts’. We have seen that visual points do exhibit spatial simplicity and hence constitute a kind of simple impressions. But I have argued that, for various reasons, there must be more to simple impressions than that spatial simplicity. The complex impression of the apple, which Hume cites straight at the beginning, shows this quite clearly. That impression is complex because it may be ‘distinguished into parts’—the apple’s colour, taste, and smell, however ‘united together’ in the apple, are ‘at least distinguishable from each other’. One can also distinguish this apple into, say, a right and a left half, and even actually chop it into halves and quarters. Now, it is evident that colour, taste and smell, however distinguishable from each other, are not ‘parts’ of the apple in the same sense as the quarters into which I can chop it.12 It appears that on a number of occasions when talking about simple perceptions Hume uses the term ‘parts’ not literally, but metaphorically: these ‘parts’ should more appropriately be called ‘aspects’.13 Otherwise, in fact, it is not even entirely clear that simple and complex perceptions as defined by Hume—the ones as ‘admit[ting] of no distinction nor separation’, the others as ‘distinguish[able] into parts’—are a genuine pair of foils. It is now, I think, time to investigate more closely the other side of Hume’s definition of simple perceptions, to which, after all, he seems to stick with admirable consistency: that according to which they do not admit of any distinction or separation. This part of Hume’s definition singles out as simple some rather unexpected perceptions. For example, while presenting the gold mountain as a fiction of the imagination that does, however, contain the possibility of existence, Hume contrasts it with a mountain without a valley, which is inconceivable because, he says, ‘we can form no idea of a mountain without a valley’ (T32). Now, if simple ideas are ‘such as admit of no distinction nor separation’, it seems to follow that the idea of the mountain + valley set, constituted by such complex ideas as those of mountain and of valley, is, according to that definition, ‘simple’. In a somewhat similar vein: when a globe of white marble is presented, we receive only the impression of a white colour dispos’d in a certain form, nor are we able to separate and distinguish the colour from the form (T25). Like the mountain and the valley, the colour and shape of the white globe are inseparable. In this sense, the white globe too is an example of a simple impression—and as such Hume presents it.

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See D. G. C. McNabb, David Hume. His Theory of Knowledge and Morality, London: Hutchinson University Library, 1951, p. 28. Similarly, the idea of man is logically complex, involving the (logical) parts ‘animal’ and ‘rational’; and spatially complex, because it has as its (spatial) parts the ideas of a head, of a torso, of legs, etc. (as J. Bennett put it in his Locke Berkeley Hume Central Themes, 1971, p. 242). 13

The point that in treating ‘complex ideas as divisible into parts, he is thinking metaphorically’ is made by D. Pears, Hume’s System. An Examination of the First Book of His Treatise, Oxford: Oxford University Press, 1990, p. 20. 11

This baffling sort of simple perceptions becomes particularly interesting in connection with Hume’s repeatedly stated theory that, for all their simplicity, simple ideas can resemble each other: ’Tis evident, that even different simple ideas may have a similarity or resemblance to each other; nor is it necessary, that the point or circumstance of resemblance shou’d be distinct or separable from that in which they differ. Blue and green are different simple ideas, but are more resembling than blue and scarlet; tho’ their perfect simplicity excludes all possibility of separation or distinction. ’Tis the same case with particular sounds, and tastes and smells… (T/637).14 It is important to note that the example here does not focus directly on the resemblance between blue and green, but rather uncovers it by triangulating blue, green and scarlet. The resemblance between the two simple ideas is identified not in its own right, but only within a pattern of relative resemblances . The case of the globe of white marble is used to elaborate on precisely the same issue: we come to ‘distinguishing the figure from the body figur’d’, which are ‘in reality neither distinguishable, nor different, nor separable’, because ‘in this simplicity there may be contain’d many different resemblances and relations’. After stating that the white globe is simple in that its colour and shape cannot be separated or distinguished, Hume proceeds by indicating that nevertheless … observing afterwards a globe of black marble and a cube of white, and comparing them with our former object, we find two separate resemblances, in what formerly seem’d, and in reality is, perfectly inseparable … we shou’d consider the figure and colour together, but still keep in our eye the resemblance to the globe of black marble, or that to any other globe of whatever colour or substance. (T25). This is what Hume calls ‘distinctio rationis’, the operation of making through our reason distinctions within what is in reality inseparable. The white globe, the back globe and the white cube are, we are told, simple; and yet they are linked together in a chain of resemblances. These result from reflecting on the operations the mind performed when it perceived first the two globes, and then the two white bodies. In other words, the resemblances between the white globe and cube and the white and black globe are not just given, but seem to emerge as a result of our reason’s reflection on the patterns created by its own selective attention.15

14

On this passage A. Reinach, ‘Kant’s interpretation of Hume’s problem’, in K. R. Merrill and R. W. Shahan (eds.), David Hume, Many-Sided Genius, Norman: University of Oklahoma Press, 1976, pp. 161-88, p. 168; see also Space and the Self, pp. 178–183. On resemblance between simple perceptions see R. Butler’s excellent ‘Distinctio Rationis, or the Cheshire Cat which left its smile behind it’, Proceedings of the Aristotelian Society, N.S. 76, 1976, pp. 165–176, and ‘Hume's impressions’, in G. Vesey (ed.), Impressions of Empiricism, Royal Institute of Philosophy Lectures, vol. 9, 1974–1975, London: Macmillan, 1976, pp. 122–136. 15

See Butler, ‘Distinctio Rationis’ and ‘Hume’s impressions’. 12

The simplicity of the impressions of these white globes, cubes etc. seems to be key to the argument, and it is now worth looking into it in more detail. The problem is, of course, the obvious spatial complexity of globes and cubes. I indicate earlier that spatial extension seemed a reasonable, if not a strictly necessary assumption for the impression and idea of red, or for the ideas of blue, green and scarlet that Hume mentions as examples of simplicity. The case of the impressions of the globes and cubes is different: spatial complexity is actually essential to them. The round shape of the globe of white marble is actually one of the objects explicitly under consideration. Don Garrett suggested that the impression of the white globe is ‘simple’ insofar as it is a collection of white minima sensibilia that all look the same; each of them can therefore be taken, in his view, as a token of the same type.16 Indeed, according to this argument the sphere itself is just another such token together with the individual minima sensibilia, only on a different scale.17 I do not find this highly ingenious idea entirely convincing. For Hume is not talking about a homogeneously lighted white circle, but of a white sphere. Unlike the disk, a sphere is shaded, and as such it is distinctly not a collection of white minima sensibilia all looking exactly like each other. Nor is it very likely that Hume could have taken this particular wrong view, since the topic was standard since the discussion, first by Locke in the second edition of the Essay, then by Berkeley and numerous others, of Molyneux’s question.18 Moreover, this reading leaves out the case of the white cube, which Hume’s discussion evidently assumes is as simple as the white globe.

16

In p. 247 fn 4, Garrett reports of a private exchange with Jonathan Bennett in connection with Locke’s lack of consistency on the issue of simplicity. In this connection he cites Locke’s Essay, Book 2, ch. 15, §9: ‘none of the distinct ideas we have of either [space or time] is without all manner of composition: It is the very nature of both of them to consist of parts: But their parts being all of the same kind, and without the mixture of any other idea, hinder them not from having a place amongst the simple ideas’. As Garrett indicates, in Book 2, ch. 12, §5 ‘this kind of composition is exactly what Locke declares to be sufficient to make an idea a “simple mode”, which is a kind of complex idea’. The same also obtains for the ideas of power, extension, etc. The passage from Locke is also interesting as background for Hume’s T221. 17

See below, §5, for the similarity between this reading and the way Hume presents the cases of the grain of sand and its parts and of the insect a thousand times less than a mite. It may be worth adding, however, that the discussions of the white sphere, of the grain of sand and of the insect, which appear within the same few pages in Book 1 of the Treatise (T25 and T27– 8) are not cross-referred to in any way. 18

The Irish medic William Molyneux famously wrote to Locke asking whether in his view a newly sighted man would be able immediately to identify by vision a cube and a sphere he was formerly acquainted with by touch: see Locke, Essay Concerning Human Understanding (Book 2, ch. 9, §8). Berkeley’s (negative) response is in the New Theory of Vision, §§130ff. The debate on the issue was very wide. For a contextual and cultural assessment, see the classic study by M. J. Morgan, Molyneux's Question: Vision, Touch and the Philosophy of Perception, Cambridge: Cambridge University Press, 1977, and the more recent J. Riskin, Science in the Age of Sensibility: The Sentimental Empiricists of the French Enlightenment, Chicago and London: University of Chicago Press, 2002, ch. 2 ‘ The blind and the mathematically inclined’, pp. 19–67. For a most stimulating discussion of the philosophical 13

This said, the way in which spatial complexity is essential to the perception of the white globe is the reason why Hume regards that perception as simple. Consider: why and how is a white marble globe supposed to be different from the apple Hume cites as the very example of complexity?19 After all, in describing the colour, taste and smell of the apple Hume says that they are ‘at least distinguishable from each other’—he is, in other words, cautiously avoiding a positive statement to the effect that those qualities are actually separable. He seems, even in that case, to be invoking a distinction of reason! Let us focus on Hume’s actual treatment of these two cases. In the case of the globe, the qualities mentioned are only the whiteness and figure. These qualities are spatial, with a clear emphasis on the visual thanks to the presence of the colour element. Moreover, the body in question is a perfect geometrical solid. Even the mention of the material, marble, seems tailor-made to reinforce the impression of order and lack of any complicated emotional response. The same also applies to the other bodies Hume cites shortly afterwards, the globe of black marble and the cube of white marble that help him to trace the different patterns of resemblance linking together these ‘simple’ perceptions and giving rise to the ‘distinctions without separation’ between colour and form, figure and body figured. In sharp contrast with the tidiness of the regular geometrical shapes and the black and white in this discussion, Hume’s apple is coloured (perhaps red—as we’ve seen, the simple impression of red in the sunshine appears not much later in the text, in the following page), and rather than its round(ish) form he chooses to mention its smell and taste. The emphasis is on the richness and variety of concrete perceptions, and the argument includes a range of spatial and non-spatial sensory modalities, visual and non-visual. By contrast, the white globe, the black globe and the white cube are the barest realisations of geometric order: their simplicity is in their geometrical epistemic clarity and economy. In this sense, the marble globes and cube are as simple as the individual purple and solid points in which we can analyse the surface of Hume’s desk. The former are simple in the instant apprehension granted by geometry, like the latter are simple in their spatial indivisibility. In turn, the focus on the different patterns of resemblance linking the globe of white marble to the globe and the cube of black marble does not render them any less ‘simple’. Rather, it uncovers a different level of simplicity contained within theirs, the simplicity of their colours and shapes. It is not difficult to imagine, in a different literary context, Hume focussing on the simplicity of the very apple he used to illustrate complexity: for example, for all its colour, shape, size, and smell, the impression of the apple may be regarded as one and the same as my desire to bite it, and passions such as that desire, Hume has indicated, are simple.

issues involved see G. Evans, ‘Molyneux’s Question’, in A. Phillips (ed.), Gareth Evans: Collected Papers, Oxford: Clarendon Press, 1985, pp. 364–99. 19

L.-M. Russow, ‘Simple Ideas and Resemblance’, Philosophical Quarterly 30, 1980, 340– 50, p. 345, comments that ‘in the light of his remarks about the white globe, it seems to follow that the colour-of-the-apple-plus-the-shape-of-the-apple is a simple idea, but that the colour alone, being inseparable from the shape, is not […] Hume’s general tendency to talk about colours per se as simple ideas is not consistent with his considered analysis’. 14

§5 — Back to the points By way of a conclusion, let us briefly go back to the points Hume invokes against the doctrine of infinite divisibility. Consider again Hume’s famous passage on the grain of sand, this time in its entirety: When you tell me of the thousandth and ten thousandth part of a grain of sand, I have a distinct idea of these numbers and of their different proportions; but the images, which I form in my mind to represent the things themselves, are nothing different from each other, nor inferior to that image, by which I represent the grain of sand itself, which is suppos’d so vastly to exceed them. What consists of parts is distinguishable into them, and what is distinguishable is separable. But whatever we may imagine of the thing, the idea of a grain of sand is not distinguishable, nor separable into twenty, much less into a thousand, ten thousand, or an infinite number of different ideas (T27). Note that here, in connection with the indivisible idea of a grain of sand, there is an evident reference to the definition of simplicity via the mention of the possibility of distinction and separation. The impressions are indistinguishable; the ideas are distinct. The grain of sand is not distinguishable into its parts, so these parts cannot be conceived separately; and yet Hume is ready to acknowledge that we do have distinct ideas of the proportions between the grain of sand itself and its thousandth and ten-thousandth part. The key here is that the same mental image of a visual indivisible, presumably originally copied from impressions such as that of the spot of ink, is used by our mind, within each different scale, to represent the minimum within that scale, whether that be the grain of sands itself or any of its proportional parts. That this is the case is further clarified by the other case Hume uses to illustrate his position, that of ‘an insect a thousand times less than a mite’: … we can form ideas, which shall be no greater than the smallest atom of the animal spirits of an insect a thousand times less than a mite: And we ought rather to conclude, that the difficulty lies in enlarging our conceptions so much as to form a just notion of a mite, or even of an insect a thousand times less than a mite. For in order to form a just notion of these animals, we must have a distinct idea representing every part of them; which, according to the system of infinite divisibility, is utterly impossible, and according to that of indivisible parts or atoms, is extremely difficult, by reason of the vast number and multiplicity of these parts. (T28)20 Here the problem for our imagination is not the minuteness of the insect, but the huge number of its parts; and the minima are absolutely simple and indivisible, but within their scale. For the minimum within a scale may well, like the small insect, turn out to be a whole universe, composed of an incalculably large number of minute parts, in the next one. 20

A discussion of the implications of this position is to be found in my Space and the Self in Hume’s ‘Treatise’, ch. 1; see also ‘The Existence of External Objects in Hume’s Treatise: Realism, Scepticism, and the Task of Philosophy’, in R. Popkin and J. van der Zande (eds), The Skeptical Tradition Around 1800: Skepticism in Philosophy, Science and Society, Dordrecht: Kluwer, 1998, pp. 3–13. 15

In section 3 I examined the spatial simplicity of visual points and came to the conclusion that it does not seem to be a very promising representative for the simplicity of all our simple perceptions. In section 4 I presented an alternative view of simplicity, which followed Ronald Butler in suggesting that simplicity, just like resemblance, is not a brute fact about some of our perceptions, but rather results from our mind’s reflecting on the operations of its own selective attention. This second way of looking at simplicity has the advantage of being inclusive. By making the simplicity of perceptions depend on mental operations, it also emphasises its relativity to context. Thus it is in a position to reconcile, insofar as they are reconcilable at all, the spatial simplicity of a coloured point with the simplicity of apprehension of the white sphere as well as of the mountain + valley set, and with the simplicity of emotional response and passions. Its strength lies in acknowledging that impression and ideas are not, strictly speaking, simple per se, but always in relation to the frame of reference of complex ideas to which they partake: simplicity is, in this sense, just like indivisibility. A further advantage of this reading is that it is in a position to account for Hume’s apparent lack of interest in the simplicity of simple perceptions: for in fact there is nothing much to be interested in, aside from their being the simple elements within certain contexts. Finally, this reading finds an interesting echo in a feature of Hume’s position on the indivisible impressions and ideas he lines up against infinite divisibility. There is an odd looseness of fit between our indivisible impressions (no smaller than those of a grain of sand or of the insect) and the various orders of corresponding indivisible ideas (our ideas of the grain of sand and of its thousandth part, etc.; our idea of the insect and of the atom of its animal spirits, etc.). This forces on our mind an unexpected margin of choice that is, I think, a good image of the situation with the simplicity of simple perceptions, a family each member of which is defined, in its criteria and standards, in relation to our attention and the frame of reference within which those perceptions belong.

16