Our lives are carried forward by the intervention of what we call meat, drink and sleep. We are liable to the accidents of health and sickness. We are alternately the recipients of joy and sorrow, of cheerfulness and melancholy. Our passions are excited by similar means, whether of love or hatred, complacency or indignation, sympathy or resentment. I could fill many pages with a description of the properties or accidents, which belong to man as such, or to which he is liable. Now with all these each man is acquainted in the sphere of his inward experience, whether he is a single being standing by himself, or is an individual belonging to a numerous species. Observe then the difference between my acquaintance with the phenomena of the material universe, and with the individuals of my own species. The former say nothing to me; they are a series of events and no more; I cannot penetrate into their causes; that which gives rise to my sensations, may or may not be similar to the sensations themselves. The follower of Berkeley or Newton has satisfied himself in the negative. But the case is very different in my intercourse with my fellow-men. Agreeably to the statement already made I know the reality of human nature; for I feel the particulars that constitute it within myself. The impressions I receive from that intercourse say something to me; for they talk to me of beings like myself. My own existence becomes multiplied in infinitum. Of the possibility of matter I know nothing; but with the possibility of mind I am acquainted; for I am myself an example. I am amazed at the consistency and systematic succession of the phenomena of the material universe; though I cannot penetrate the veil which presents itself to my grosser sense, nor see effects in their causes. But I can see, in other words, I have the most cogent reasons to believe in, the causes of the phenomena that occur in my apparent intercourse with my fellow-men. What solution so natural, as that they are produced by beings like myself, the duplicates, with certain variations, of what I feel within me? The belief in the reality of matter explains nothing. Supposing it to exist, if Newton is right, no particle of extraneous matter ever touched the matter of my body; and therefore it is not just to regard it as the cause of my sensations. It would amount to no more than two systems going on at the same time by a preestablished harmony, but totally independent of and disjointed from each other.