in The Encyclopedia of Empiricism, (Greenwood Press, 1997) Don Garrett and Ed Barbanell, eds. Copyright 1997

Saul Traiger, Occidental College

SIMPLE/COMPLEX. An idea is either simple or complex. A complex idea can be separated into other ideas of which it is composed. Simple ideas are those ideas which cannot be so decomposed. Ideas received through experience are already bundled into complex ideas. For example, the idea of a white horse is a complex idea. Through ABSTRACTION, one can separate it into the ideas of white and horse. The idea of a horse, in turn, is composed of further ideas. The idea of white, however, is simple; it can't be broken down into component simpler ideas. Since all complex ideas are composed of simple ones, what is received from experience are simple ideas, typically packaged with others to form complex ideas. Thus LOCKE calls simple ideas "the Materials of all our Knowledge." (Essay, II,ii, 2)

Locke's simple ideas present "one uniform Appearance" either through sensation or reflection. Each simple idea is completely distinct from all others, including those simple ideas with which it may be conjoined in experience. Ideas of color, sound, tastes, and odors, are simple ideas of sensation received from one sense. Space, figure, rest and motion are simple ideas received from more than one sense. Pleasure, pain, power, existence and unity are simple ideas of sensation and reflection.

HUME employs the simple/complex distinction in his codification of perceptions. Simple ideas are derived from simple impressions, which they resemble. Complex ideas are composed of simple ones; a complex idea, e.g. an idea of the IMAGINATION, need not have an antecedent resembling complex impression, though each of its component simple ideas must have antecedent resembling simple impressions. Hume shares Locke's view that ideas such as the ideas of colors, tastes and sounds, are simple, but he parts company with Locke on others, such as the idea of existence. Reflection on any idea, Hume argues, is reflection on it as existent. There is no separate simple idea of existence. BERKELEY, contra Locke, holds that the idea of unity is a complex idea abstracted from all others. (Principles xiii)

While Berkeley holds that ideas can be collected and "marked by one name" or separated from such collections by abstraction, he does not claim that there are simple ideas. (Principles, i) Winkler chronicles several arguments from Berkeley's notebooks, arguments not prominent in his published works, against the simplicity of color ideas. Our ability to compare two ideas of shades of the same color, Berkeley argued, shows that they must have constituent ideas which makes the comparison possible. Thus, the ideas of the shades are not simple. Berkeley also held that the complexity of the cause of an idea of color shows that the idea itself must be complex. This second argument is open to the objection that Berkeley failed to distinguish the phenomenological character of ideas from the character of their causes.

Both Locke and Hume offer descriptions of the mental operations which give rise to complex ideas. Locke describes three kinds of complex ideas -- modes, SUBSTANCES and RELATIONS, representing three different types of complexity in ideas. With his view that our ideas of substances are complex ideas, Locke sets himself against a tradition begun by ARISTOTLE and followed by the modern rationalists, which took substances to be simple. Descartes held that the mind, for example, was a simple substance. For Locke, the notion of an immaterial substance is as much a complex idea as is any idea of material substance. Hume finds that there is no simple impression of substance; so there can be no simple idea. The idea of substance, then, is nothing but a collection of simple ideas. Hume sees a philosophical liability in the use of the notion of substance. Philosophers are likely to forget that it is just a complex idea, and to mistakenly infer that it represents a basic metaphysical category.

Primary Texts:

Aristotle, Categories, in The Complete Works of Aristotle, Vol. I, Jonathan Barnes, ed. (Princeton: Princeton University Press, 1984)

Berkeley, George, The Works of George Berkeley, Bishop of Cloyne, 9 vols. (London, 1948-57)

Descartes, Rene, The Philosophical Writings of Descartes (Cambridge: Cambridge University Press, 1984-1985)

Hume, David, A Treatise of Human Nature L.A. Selby-Bigge and P.H. Nidditch, eds., (Oxford: Oxford University Press, 1978)

Locke, John, An Essay Concerning Human Understanding, Nidditch, P. H., ed.

(Oxford : Oxford University Press, 1987)

Secondary Literature:

Ayers, Michael, Locke: Epistemology and Ontology (London: Routledge, 1991)

Winkler, Kenneth P., Berkeley: An Interpretation (Oxford: Oxford University Press, 1989)