Let us begin with the further consideration of desire. The distinction has already been pointed out between instinctive impulse and desire of that kind which is a factor in our human experience. The latter involves a consciousness of its object, which in turn implies a consciousness of self. In this consciousness of objects which is also that of self, or of self which is also a consciousness of objects, we have the distinguishing characteristic of desire (as we know it), of understanding and of will, as compared with those processes of the animal soul with which they are apt to be confused. And this consciousness is also the common basis which unites desire, understanding, and will with each other. Our habitual language for expressing the life of the soul naturally lends itself to obscure the distinction upon which it is important here to insist. We constantly speak of sensation as if it were in itself a consciousness of an object by which it is excited. We speak of feeling this thing and that, which we no doubt do feel, but which we only feel because we are self-conscious; because in feeling we distinguish ourselves from the feelings as their subject. This confusion is complicated by the common usage of feeling and consciousness as equivalent terms; which makes it difficult to mark the difference between the feeling of self, implied in all pleasure and pain, and that distinguishing presentation of self, as at once the subject of feelings and other than them, which properly constitutes self-consciousness. Nor when we have recognised the distinction between mere feeling and feeling as it is in the self-conscious man, is it easy to express it. If we use one set of terms, we fail to convey the difference between sensation, as the affection of a soul or of an individual subject properly so called, and any affection of one material thing by another. Adopting another set of terms, we seem to fall into the error just noticed, of identifying mere sensation with the consciousness of self and object. (§ 118 ¶ 1)