Locke, substance is just an idea

1. The mind is supplied with many simple ideas, which come to it through the senses from outer things or through reflection on its own activities. Sometimes it notices that a certain number of these simple ideas go constantly together, and it presumes them to belong to one thing; and—because words are suited to ordinary ways of thinking and are used for speed and convenience—those ideas when united in one subject are called by one name. Then we carelessly talk as though we had here one simple idea, though really it is a complication of many ideas together. What has happened in such a case is that, because we can’t imagine how these simple ideas could exist by themselves, we have acquired the habit of assuming that they exist in (and result from) some substratum, which we call substance. [‘Substratum’ = ‘what underlies’ = something that serves as the basis or foundation of something else.]

2. So that if you examine your notion of pure substance in general, you’ll find that your only idea of it is a supposition ofan unknown support of qualities that are able to cause simple ideas in us—qualities that are commonly called ‘accidents’.

If anyone were asked ‘What is the subject in which colour or weight inheres?’, he would have to reply ‘In the solid extended parts’; and if he were asked ‘What does that solidity and extension inhere in?’, he wouldn’t be in a much better position than the Indian philosopher who said that the world was supported by a great elephant, and when asked what the elephant rested on answered ‘A great tortoise’. Being further pressed to know what supported the broad-backed tortoise, he replied that it was something he knew not what. So too here, as in all cases where we use words without having clear and distinct ideas, we talk like children who, being asked ‘What’s this?’ about something they don’t recognize, cheerfully answer ‘It’s a thing’. Really all this means, when said by either children or adults, is that they don’t know what it is, and that ‘the thing’ they purport to know and talk about isn’t something of which they have any distinct idea at all—they are indeed perfectly in the dark about it.

So the idea of ours to which we give the general name ‘substance’, being nothing but the supposed but unknown support of those qualities we find existing and which we imagine can’t exist ‘sine re substante’ — that is, without something to support them — we call that support substantia; which, according to the true meaning of the word, is in plain English standing under or upholding. [‘Sub’ is Latin for ‘under’, and ‘stans’ is Latin for ‘standing’; so ‘substans’ (English ‘substance’) literally means something that stands under something.]

3. In this way we form an obscure and relative idea of substance in general.  (…) From this we move on to having ideas of various sorts of substances, which we form by collecting combinations of simple ideas that we find in our experience tend to go together and which we therefore suppose to flow from the particular internal constitution or unknown essence of a substance. Thus we come to have the ideas of  a man, horse, gold, water, etc. If you look into yourself, you’ll find that your only clear idea of these sorts of substances is the idea of certain simple ideas existing together.

It is the combination of ordinary qualities observable in iron, or a diamond, that makes the true complex idea of those kinds of substances—kinds that a smith or a jeweller commonly knows better than a philosopher does. Whatever technical use he may make of the term ‘substance’, the philosopher or scientist has no idea of iron or diamond except what is provided by a collection of the simple ideas that are to be found in them—with •one further ingredient. complex ideas of substances are made up of those simple ideas plus •the confused idea of some thing to which they belong and in which they exist. So when we speak of any sort of substance, we say it is a thing having such or such qualities: body is a thing that is extended, shaped, and capable of motion;•spirit, a thing that can think; and we say that hardness and power to attract iron are qualities to be found in a loadstone,·conceived of as a thing containing these qualities·. [Loadstone is a kind of rock that is naturally magnetic.] These and similar ways of speaking show that the substance is always thought of as some thing in addition to the extension, shape, solidity, motion, thinking, or other observable ideas, though we don’t know what it is. [Locke uses •‘spirit’, as he does ‘soul’, to mean merely ‘thing that thinks’ or ‘thing that has mental properties’. It doesn’t mean something spiritual in any current sense of the term.]

4. So when we talk or think of any particular sort of corporeal substances—e.g. horse, stone, etc.—although our idea of it is nothing but the collection of simple ideas of qualities that we usually find united in the thing called ‘horse’ or ‘stone’, still we think of these qualities as existing in and supported by some common subject; and we give this support the name ‘substance’, though we have no clear or distinct idea of what it is. We are led to think in this way because we can’t conceive how qualities could exist unsupported or with only one another for support.

5. The same thing happens concerning the operations of the mind—thinking, reasoning, fearing, etc. These can’t exist by themselves, we think, nor can we see how they could belong to body or be produced by it; so we are apt to think that they are the actions of some other substance, which we call ‘spirit’.  We have as clear a notion of the substance of •spirit as we have of •body. The latter is supposed (without knowing what it is) to be •the substratum of those simple ideas that come to us from the outside, and the former is supposed (still not knowing what it is) to be •the substratum of the mental operations we experience within ourselves. Clearly, then, we have as poor a grasp of the idea of bodily substance as we have of spiritual substance or spirit. So we shouldn’t infer that there is no such thing as spirit because we have no notion of the substance of spirit, any more than we should conclude that there is no such thing as body because we have no clear and distinct idea of the substance of matter.

6. Whatever the secret, abstract nature of substance in general may be, therefore, all our ideas of particular sorts of substances are nothing but combinations of simple ideas co-existing in some unknown cause of their union. We represent particular sorts of substances to ourselves through such combinations of simple ideas, and in no other way. They are the only ideas we have of the various sorts of things—the sorts that we signify to other people by means of such names as ‘man’, ‘horse’, ‘sun’, ‘water’, ‘iron’. Anyone who hears such a word, and understands the language, forms in his mind a combination of those simple ideas that he has found—or thinks he has found—to exist together under that name; all of which he supposes to rest in and be fixed to that unknown common subject that doesn’t inhere in anything else in its turn. Consider for instance the idea of the sun: it is merely a collection of the simple ideas, bright, hot, roundish, having a constant regular motion, at a certain distance from us—and perhaps a few others, depending on how accurately the owner of the idea has observed the properties of the sun.

7. The most perfect idea of any particular sort of substance results from putting together most of the simple ideas that do exist in it—·i.e. in substances of that sort·—including its active powers and passive capacities. (These are not simple ideas, but for brevity’s sake let us here pretend that they are.) Thus the complex idea of the substance that we call a loadstone has as a part the power of attracting iron; and a power to be attracted by a loadstone is a part of the complex idea we call ‘iron’. These powers are counted as inherent qualities of the things that have them. Every substance is as likely, through the powers we observe in it, (a) to change the perceptible qualities of other subjects as (b) to produce in us those simple ideas that we receive immediately from it. When (b) happens with fire (say), our senses perceive in fire its heat and colour, which are really only the fire’s powers to produce those ideas in us. When (a) happens, we also learn about the fire because it acts on us mediately [= ‘through an intermediary’] by turning wood into charcoal and thereby altering how the wood affects our senses. . . . In what follows, I shall sometimes include these powers among the simple ideas that we gather together in our minds when we think of particular substances. Of course they aren’t really simple; but they are simpler than the complex ideas of kinds of substance, of which they are merely parts.

8. It isn’t surprising that powers loom large in our complex ideas of substances. We mostly distinguish substances one from another through their secondary qualities, which make a large part of our complex ideas of substances . (Our senses will not let us learn the sizes, textures, and shapes of the minute parts of bodies on which their real constitutions and differences depend; so we are thrown back on using their secondary qualities as bases for distinguishing them one from another.) And all the secondary qualities, as has been shown ·in viii·, are nothing but powers. . . .