Locke, John (1632–1704)

DOI: 10.4324/9780415249126-DA054-2
Version: v2,  Published online: 2017
Retrieved December 13, 2018, from

3. The understanding and ideas

According to Locke, in order to establish the foundations of knowledge we need experience. Experience is twofold. It includes the perception of external, sensible objects and the perception of the internal operations of our minds: ‘These two are the fountains of knowledge, from whence all the ideas we have, or can naturally have, do spring’ (Essay II.i.2). There is another source of beliefs, namely revelation, but there is no other source of ideas.

All ideas are either simple or complex. Simple ideas are of ‘one uniform appearance’ and cannot be broken down into different ideas (Essay II.ii.i). Ideas are acquired only from passive experience and the names of simple ideas are indefinable (Essay III.iv.7). Examples are our ideas of yellow, hard and bitter. Complex ideas are composed by joining simple ideas. Examples are the ideas of a man, an army, the universe (Essay II.xii.1). Scholars disagree as to whether Locke thought that we can also acquire complex ideas immediately via experience or whether the senses and reflection deliver only simple ideas which are subsequently put together by the understanding to form complex ideas. But there is no doubt that he uses these basic notions to develop a combinatorial theory of ideas of great power and philosophical sophistication.

For example, one species of complex ideas is our ideas of particular sorts of substances. We have the idea of gold and this, according to Locke, is a combination of the ideas of yellow, heavy, ductile and malleable. It does seem, however, there is something more to the particular substances that we encounter through our senses than just the cluster of properties that gives rise to constituents of the complex idea. There seems to be some underlying thing that binds or unifies these properties together, something in which these properties inhere. This presents a problem for Locke’s theory because we cannot immediately sense that underlying thing or substratum. We seem to have the idea of an underlying substance in general, but we do not have direct epistemic access to it. What sort of thing might it be?

Scholars of Locke’s thought have offered various interpretations of the nature of this substance in general, or substratum. Some claim that it is a generic kind of stuff, perhaps the matter of the corpuscular philosophers, such as Robert Boyle, or the prime matter of Aristotle. Others claim that there are two types of substance in general, material substance and spiritual substance. Still others have claimed that Locke’s substratum is just the microstructure or real essence (to be discussed in §4) of the particular substance in question. The traditional and most widely held view, however, is that, for Locke, substance in general is that in which properties inhere, which subsists in itself, and which gives each particular substance its particularity and that this is all we know about it. Locke does not have a theory of substance as such, but he is committed to it as an ontological category: it is part of his inventory of being ‘though we know not what it is’ (Essay II.xxiii.3).

Another species of complex ideas is what Locke calls modes. Here, it should be pointed out, Locke’s terminology is idiosyncratic. Amongst his immediate predecessors and contemporaries the term ‘mode’ referred to modifications of substance. Thus, for Descartes, shape is a modification of material substance and therefore shape is a mode of matter. While Locke accepted the ontological category of mode, his primary use of the term ‘mode’ is to refer to a species of complex idea. These ideas come in two forms, simple and mixed. Simple modes are formed by iteration of the very same idea. Thus the natural numbers are formed by iteration of the simple idea of unity.

Mixed modes, by contrast, are combinations of different ideas. He gives the examples of murder and wrestling. All of our moral ideas are mixed modes. Thus, there are some parallels between mathematics and morality and, in fact, Locke claimed that we can have a demonstrative science of each (Essay III.xi.16). By this he means a science of morality that, just like geometry, is founded upon a set of axioms. Locke never developed a demonstrative science of morality, in spite of the urging of some of his friends.

This is not to claim, however, that geometry and morality are both sciences of the mind that are completely unconnected with experience. For, Locke claims that what makes our geometrical ideas true is the nature of (Euclidean) space. Furthermore, he claims that we acquire some of our mixed moral modes from experience. Some of our mixed modal ideas are purely creations of our minds, whereas others, such as hypocrisy, derive from experience, though their archetypes are normally transient events such as a particular lie or murder (Essay II.xxii.2).

In addition to complex ideas of substances and complex modal ideas, we can have ideas of relations such as identity, resemblance and particular powers. Locke puts the notions of identity and resemblance to work in his theory of persons and his theory of qualities, as we shall see in §8. Yet there is another facet of complex ideas that Locke regards as unique to humans and this is our ability to form general or abstract ideas.

Citing this article:
Anstey, Peter. The understanding and ideas. Locke, John (1632–1704), 2017, doi:10.4324/9780415249126-DA054-2. Routledge Encyclopedia of Philosophy, Taylor and Francis,
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