The whole of this terminology must now be considered as having simply a conventional value, and must be set aside for the present. These are the precise terms in which this question presents itself to my mind. A part of the knowable consists in sensations. We must, therefore, without troubling to style this aggregate of sensations _matter_ rather than _mind_, make an analysis of the phenomena known by the name of mind, and see whether they differ from the preceding ones. Let us, therefore, make an inventory of mind. By the process of enumeration, we find quoted as psychological phenomena, the sensations, the perceptions, the ideas, the recollections, the reasonings, the emotions, the desires, the imaginations, and the acts of attention and of will. These appear to be, at the first glance, the elements of mind; but, on reflection, one perceives that these elements belong to two distinct categories, of which it is easy to recognise the duality, although, in fact and in reality, these two elements are constantly combined. The first of these elements may receive the generic name of objects of cognition, or objects known, and the second that of acts of cognition. Here are a few examples of concrete facts, which only require a rapid analysis to make their double nature plain. In a sensation which we feel are two things: a particular state, or an object which one knows, and the act of knowing it, of feeling it, of taking cognisance of it; in other words, every sensation comprises an impression and a cognition. In a recollection there is, in like manner, a certain image of the past and the fact consisting in the taking cognisance of this image. It is, in other terms, the distinction between the intelligence and the object. Similarly, all reasoning has an object; there must be matter on which to reason, whether this matter be supplied by the facts or the ideas. Again, a desire, a volition, an act of reflection, has need of a point of application. One does not will in the air, one wills something; one does not reflect in the void, one reflects over a fact or over some difficulty. We may then provisionally distinguish in an inventory of the mind a something which is perceived, understood, desired, or willed, and, beyond that, the fact of perceiving, of understanding, or desiring, or of willing. To illustrate this distinction by an example, I shall say that an analogous separation can be effected in an act of vision, by showing that the act of vision, which is a concrete operation, comprises two distinct elements: the object seen and the eye which sees. But this is, of course, only a rough comparison, of which we shall soon see the imperfections when we are further advanced in the study of the question.