Having premised so much, we observe that all these sciences which form the subject of logic are but collections of propositions, and that each proposition merely connects or separates a subject and an attribute, that is, two names, a quality and a substance; that is to say, a thing and another thing. We must then ask what we understand by a thing, what we indicate by a name; in other words, what it is we recognize in objects, what we connect or separate, what is the subject-matter of all our propositions and all our science. There is a point in which all our several items of knowledge resemble one another. There is a common element which, continually repeated, constitutes all our ideas. There is, as it were, a minute primitive crystal which, indefinitely and variously repeating itself, forms the whole mass, and which, once known, teaches us beforehand the laws and composition of the complex bodies which it has formed.
Now, when we attentively consider the idea which we form of anything, what do we find in it? Take first, substances: that is to say, Bodies and Minds.[398] This table is brown, long, wide, three feet high, judging by the eye: that is, it forms a little spot in the field of vision; in other words, it produces a certain sensation on the optic nerve. It weighs ten pounds: that is, it would require to lift it an effort less than for a weight of eleven pounds, and greater than for a weight of nine pounds; in other words, it produces a certain muscular sensation. It is hard and square, which means that, if first pushed, and then run over by the hand, it will excite two distinct kinds of muscular sensations. And so on. When I examine closely what I know of it, I find that I know nothing else except the impressions it makes upon me. Our idea of a body comprises nothing else than this: we know nothing of it but the sensations it excites in us; we determine it by the nature, number, and order of these sensations; we know nothing of its inner nature, nor whether it has one; we simply affirm that it is the unknown cause of these sensations. When we say that a body has existed in the absence of our sensations we mean simply that if, during that time, we had been within reach of it, we should have had sensations which we have not had. We never define it save by our present or past, future or possible, complex or simple impressions. This is so true, that philosophers like Berkeley have maintained, with some show of truth, that matter is a creature of the imagination, and that the whole universe of sense is reducible to an order of sensations. It is at least so, as far as our knowledge is concerned; and the judgments which compose our sciences have reference only to the impressions by which things are manifested to us.
So, again, with the mind. We may well admit that there is in us a soul, an "ego," a subject or recipient of our sensations, and of our other modes of being, distinct from those sensations and modes of existence; but we know nothing of it. Mr. Mill says:
"For, as our conception of a body is that of an unknown exciting cause of sensations, so our conception of a mind is that of an unknown recipient, or percipient, of them; and not of them alone, but of all our other feelings. As body is the mysterious something which excites the mind to feel, so mind is the mysterious something which feels, and thinks. It is unnecessary to give in the case of mind, as we gave in the case of matter, a particular statement of the sceptical system by which its existence as a Thing in itself, distinct from the series of what are denominated its states, is called in question. But it is necessary to remark, that on the inmost nature of the thinking principle, as well as on the inmost nature of matter, we are, and with our faculties must always remain, entirely in the dark. All which we are aware of, even in our own minds, is a certain 'thread of consciousness'; a series of feelings, that is, of sensations, thoughts, emotions, and volitions, more or less numerous and complicated."[399]
We have no clearer idea of mind than of matter; we can say nothing more about it than about matter. So that substances, of whatever kind, bodies or minds, within or without us, are never for us more than tissues, more or less complex, more or less regular, of which our impressions and modes of being form all the threads.
This is still more evident in the case of attributes than of substances. When I say that snow is white, I mean that, when snow is presented to my sight, I have the sensation of whiteness. When I say that fire is hot, I mean that, when near the fire, I have the sensation of heat. We call a mind devout, superstitious, meditative, or gay, simply meaning that the ideas, the emotions, the volitions, designated by these words, recur frequently in the series of its modes of being.[400] When we say that bodies are heavy, divisible, movable, we mean simply that, left to themselves, they will fall; when cut, they will separate; or, when pushed, they will move: that is, under such and such circumstances they will produce such and such a sensation in our muscles, or our sight. An attribute always designates a mode of our being, or a series of our modes of being. In vain we disguise these modes by grouping, concealing them under abstract words, dividing and transforming them, so that we are frequently puzzled to recognize them: whenever we pierce to the basis of our words and ideas, we find them and nothing but them. Mill says:
"Take the following example: A generous person is worthy of honour. Who would expect to recognize here a case of coexistence between phenomena? But so it is. The attribute which causes a person to be termed generous is ascribed to him on the ground of states of his mind, and particulars of his conduct; both are phenomena; the former are facts of internal consciousness, the latter, so far as distinct from the former, are physical facts, or perceptions of the senses. Worthy of honour, admits of a similar analysis. Honour, as here used, means a state of approving and admiring emotion, followed on occasion by corresponding outward acts. 'Worthy of honour' connotes all this, together with an approval of the act of showing honour. All these are phenomena; states of internal consciousness, accompanied or followed by physical facts. When we say, A generous person is worthy of honour, we affirm coexistence between the two complicated phenomena connoted by the two terms respectively. We affirm, that wherever and whenever the inward feelings and outward facts implied in the word generosity have place, then and there the existence and manifestation of an inward feeling, honour, would be followed in our minds by another inward feeling, approval."[401]
In vain we turn about as we please, we remain still in the same circle. Whether the object be an attribute or a substance, complex or abstract, compound or simple, its material is to us always the same; it is made up only of our modes of being. Our mind is to nature what a thermometer is to a boiler: we define the properties of nature by the impressions of our mind, as we indicate the conditions of the boiling water by the changes of the thermometer. Of both we know but condition and changes; both are made up of isolated and transient facts; a thing is for us but an aggregate of phenomena. These are the sole elements of our knowledge: consequently the whole effort of science will be to link facts to facts.