Let us look at it a little more closely. Knowing is a relation which unites two things, one the mind that knows, the other the thing known. In every act of knowing, something is present to the mind; if knowing is simply awareness of this actually present something, we call it immediate experience, we are acquainted with the object. But our knowledge is not only of objects {82} immediately present to the mind and with which we are therefore acquainted. Knowledge embraces the past and future and the distant realms of space. Indeed were knowledge only of what is actually present to the mind, it is difficult to imagine that we could, in the ordinary meaning of the word, know anything at all. I may be thinking, for example, of an absent friend; all that is present to my mind is, it may be, a memory image, a faint recall of his appearance on some one occasion, or perhaps a recollection of the tone of his voice, or it may be the black marks on white paper which I recognise as his handwriting. This image is present to my mind, but the image is not the object, my friend, about whom I think and make endless judgments, true and false. So also, if what is present to the mind is affecting me through the external senses, if it is a sense impression, it is clear that what is actually present is not the whole object of which I am aware, but only a very small part of it, or, it may be, no part of it at all, but something, a sound, or an odour, that represents it. The immediate data of consciousness are named by some philosophers sense data, by others, presentations, by others images, and there is much controversy as to their nature and existence, but with this controversy we are not here concerned--we are seeking to make clear an obvious distinction, namely, the distinction between knowledge by acquaintance and knowledge by description.