Leibniz, Gottfried Wilhelm (1646–1716)

DOI: 10.4324/9780415249126-DA052-1
Version: v1,  Published online: 1998
Retrieved January 23, 2019, from

8. Epistemology: ideas and sensation

Despite the fact that Leibniz is usually categorized as a continental rationalist, his main interest was not epistemological. At the same time, he did contribute to the discussions of his day on questions relating to ideas and knowledge.

In the New Essays (II.1.1), Leibniz defines an idea as follows: ‘an idea is an immediate inner object [which] expresses the nature or qualities of things’. He emphasizes that we can think that we have an idea when we do not really have one. So, for example, there can be no idea of a fastest motion because the notion is incoherent. But, he notes, ‘At first glance we might seem to have the idea of a fastest motion, for we certainly understand what we say; but yet we certainly have no idea of impossible things’. Mistaking our comprehension of the phrase ‘fastest motion’ for having a genuine idea can lead us into contradiction in this case. But in other cases, for example in mathematics, where we often use symbols without fixing ideas to them, we often must work symbolically because of the complexity of working directly with ideas themselves. In this sense one can have thought and even reasoning when we do not have ideas in the proper sense. This observation is connected with a distinction Leibniz drew between real and nominal definitions. A nominal definition is a definition in which one can doubt whether or not the notion defined is genuinely possible; a real definition is one in which the possibility of the notion defined has been established. One can thus say that it is only of real definitions that one can be sure that they correspond to a genuine idea (Meditations [1684a] 1989: 25–6; Discourse §24).

Leibniz was a supporter of innate ideas in a number of senses. First of all, he argued that there are certain particular ideas that are innate to the mind, and do not or cannot come through the senses: ‘The ideas of being, possible, and same are so thoroughly innate that they enter into all our thoughts and reasoning, and I regard them as essential to our minds’ (New Essays I.3.3). He made a similar claim for other notions, such as infinity (New Essays II.17.3). In this connection he used his celebrated marble analogy in the preface to the New Essays. Ideas and truths are in the mind, he argued, just as the shape of Hercules might already be in the veins of a block of marble, making that shape more likely to emerge when the sculptor begins to hammer on it, even though considerable effort may be required to expose the shape: ‘This is how ideas and truths are innate in us – as inclinations, dispositions, tendencies, or natural potentialities’.

Leibniz’s metaphysics, however, committed him to a stronger position still, that every idea is innate, strictly speaking, since nothing can enter a mind from the outside. He wrote: ‘The mind always expresses all its future thoughts and already thinks confusedly about everything it will ever think about distinctly. And nothing can be taught to us whose idea we do not already have in our mind’ (Discourse §26). But even though all ideas are strictly innate, Leibniz could distinguish between the ideas of sensation that in a certain sense come to us from outside, and the ideas that do not and cannot do so. As with the explication of physical causality in the context of a view in which there can be no real metaphysical causality between finite things, Leibniz could say that ‘we receive knowledge from the outside by way of the senses, because some external things contain or express more particularly the reasons that determine our soul to certain thoughts’ (Discourse §27).

Sensations are distinguished from other notions not only by their causal origin (in Leibniz’s somewhat extended sense), but also by the fact that they are confused, in contrast to the distinct notions one uses, say, in mathematics. A notion is distinct when one has ‘marks and tests sufficient to distinguish a thing from all other similar’ things; distinct notions include number, magnitude, shape and so on. A notion is confused ‘when I cannot enumerate one by one marks sufficient for differentiating a thing from others, even though the thing does indeed have such marks and requisites into which its notion can be resolved’. In this sense ‘colours, smells, tastes, and other particular objects of the senses’ are confused (Meditations [1684a] 1989: 24). Indeed, they are the confused perception of the geometrical properties of bodies that, on the mechanist programme, ground the perception of sensible qualities. ‘When we perceive colours or smells, we certainly have no perception other than that of shapes and of motions, though so very numerous and so very small that our mind cannot distinctly consider each individual one in this, its present state, and thus does not notice that its perception is composed of perceptions of minute shapes and motions alone’ (Meditations [1684a] 1989: 27). Elsewhere Leibniz used the analogy of a wave to understand this phenomenon. When we hear the roar of the ocean, we are actually hearing just a large number of individual waves, lapping on the shore. But since we cannot distinguish the sounds each individual wave makes, we hear it as an undifferentiated roar. This is just the way the confused perception of the corpuscular microstructure of bodies results in our sensation of colour, taste and so on (New Essays 1704: preface). In this way Leibniz rejected the claim that the connection between a particular sensation and its mechanical cause is the result of a perfectly arbitrary divine decree; by the Principle of Sufficient Reason, there can be no such arbitrariness in the world (New Essays II.8.13 and following, IV.6.7). Thus, it would seem, the distinction between sensations and ideas of the intellect is not a matter of kind, but a matter of degree, degree of distinctness and confusion.

An important part of this account of sensation was Leibniz’s doctrine of petites perceptions (minute perceptions). Like Descartes, Leibniz believed that we think all the time. However, unlike Descartes, he denied that we are always conscious of what we think. He held that ‘at every moment there is in us an infinity of perceptions, unaccompanied by awareness or reflection; that is, of alterations in the soul itself, of which we are unaware because these impressions are either too minute and too numerous, or else too unvarying, so that they are not sufficiently distinctive on their own’ (New Essays preface). Though we do not apperceive (that is, consciously perceive) each of them individually, these unconscious perceptions have their effects on us. They are what underlie and explain sensation, as suggested earlier. Furthermore, they also have their effect on the conscious choices that we make (New Essays II.20.6).

Finally, Leibniz also had a clear position in the debate then raging in the intellectual world over Malebranche’s view that we see all things in God, that is, that ideas do not exist in finite minds, but only in the mind of God, where they are seen by finite intellects without actually being in them (see Malebranche, N. §2). Leibniz quite clearly rejected Malebranche’s view: ‘Even if we were to see everything in God, it would nevertheless be necessary that we also have our own ideas, that is, not little copies of God’s, as it were, but affections or modifications of our mind corresponding to that very thing we perceived in God’ (Meditations [1684a] 1989: 27; compare Discourse §29).

Citing this article:
Garber, Daniel. Epistemology: ideas and sensation. Leibniz, Gottfried Wilhelm (1646–1716), 1998, doi:10.4324/9780415249126-DA052-1. Routledge Encyclopedia of Philosophy, Taylor and Francis,
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