fragment on 'Power,' in 1792, which was his last expression of reflective thought. The Philosophy of Perception and the Philosophy of Causation—our common sense of extended reality in our first intercourse with it in the senses, and our common sense conception of 'power' and 'cause' which arises in the presence of the changes amidst which we live and have our being—these were the two poles of Reid's philosophical life. His whole life was a war against two common errors of philosophers regarding these, from the days of Plato to our own, in each of which the seeds of speculative and practical scepticism seemed to lie thickly. If these two fundamental convictions were untrustworthy, then faith in anything must lose its sustaining strength. For our perceptions through the five senses are the first principles of all our reasonings about the actual universe, and our causal judgments are the means of interpreting the realities to which those perceptions only introduce us.
We find ourselves continually in contact and collision with Power that is external to ourselves individually; and we seem, too, to be exerting powers of our own: on the Power latent in the universe, our happiness or misery, our whole destiny, depends. What does all this mean? What is meant by the judgment that all changes in the universe are 'caused'; and what is the origin of this judgment, or of the conception of 'cause' that is involved in it? Are the powers which we recognise in us and around us to be referred only to inanimate things as their centres; or only to living and self-conscious persons; or to both?
Priestley, as an advocate of the claim of matter to account sufficiently for self-conscious life in man, and Kames and Priestley by their universal necessity, confirmed Reid's disposition to inquire further into the nature and
