Suppose that I accidentally prick my finger with a pin.  I immediately become aware of a condition of my consciousness—­a feeling which I term pain.  I have no doubt whatever that the feeling is in myself alone; and if anyone were to say that the pain I feel is something which inheres in the needle, as one of the qualities of the substance of the needle, we should all laugh at the absurdity of the phraseology.  In fact, it is utterly impossible to conceive pain except as a state of consciousness.

Hence, so far as pain is concerned, it is sufficiently obvious that Berkeley’s phraseology is strictly applicable to our power of conceiving its existence—­“its being is to be perceived or known,” and “so long as it is not actually perceived by me, or does not exist in my mind, or that of any other created spirit, it must either have no existence at all, or else subsist in the mind of some eternal spirit.”

So much for pain.  Now let us consider an ordinary sensation.  Let the point of the pin be gently rested upon the skin, and I become aware of a feeling or condition of consciousness quite different from the former—­the sensation of what I call “touch.”  Nevertheless this touch is plainly just as much in myself as the pain was.  I cannot for a moment conceive this something which I call touch as existing apart from myself, or a being capable of the same feelings as myself.  And the same reasoning applies to all the other simple sensations.  A moment’s reflection is sufficient to convince one that the smell, and the taste, and the yellowness, of which we become aware when an orange is smelt, tasted, and seen, are as completely states of our consciousness as is the pain which arises if the orange happens to be too sour.  Nor is it less clear that every sound is a state of the consciousness of him who hears it.  If the universe contained only blind and deaf beings, it is impossible for us to imagine but that darkness and silence should reign everywhere.

It is undoubtedly true, then, of all the simple sensations that, as Berkeley says, their “esse is percipi”—­their being is to be “perceived or known.”  But that which perceives, or knows, is mind or spirit; and therefore that knowledge which the senses give us is, after all, a knowledge of spiritual phenomena.

All this was explicitly or implicitly admitted, and, indeed, insisted upon, by Berkeley’s contemporaries, and by no one more strongly than by Locke, who terms smells, tastes, colours, sounds, and the like, “secondary qualities,” and observes, with respect to these “secondary qualities,” that “whatever reality we by mistake attribute to them [they] are in truth nothing in the objects themselves.”