In the _Commonplace Book_ we see the youth at Trinity College forging the weapons which he was soon to direct against the materialism and scepticism of the generation into which he was born. Here are rough drafts, crude hints of intended arguments, probing of unphilosophical mathematicians—even Newton and Descartes, memoranda of facts, more or less relevant, on their way into the _Essay on Vision_ and the treatise on _Principles_—seeds of the philosophy that was to be gradually unfolded in his life and in his books. We watch the intrepid thinker, notwithstanding the inexperience of youth, more disposed to give battle to mathematicians and metaphysicians than to submit even provisionally to any human authority. It does not seem that his scholarship or philosophical learning was extensive. Descartes, Malebranche, and Locke were his intimates; Hobbes and Spinoza were not unknown to him; Newton and some lesser lights among the mathematicians are often confronted. He is more rarely in company with the ancients or the mediaevalists. No deep study of Aristotle appears, and there is even a disposition to disparage Plato. He seeks for his home in the “new philosophy” of experience; without anticipations of Kant, as the critic of what is presupposed in the scientific reliability of any experience, against whom his almost blind zeal against abstractions would have set him at this early stage. “Pure intellect I understand not at all,” is one of his entries. He asks himself, “What becomes of the _aeternae veritates_?” and his reply is, “They vanish.” When he tells himself that “we must with the mob place certainty in the senses,” the words are apt to suggest that the senses are our only source of knowledge, but I suppose his meaning is that the senses must be trustworthy, as ’the mob’ assume. Yet occasionally he uses language which looks like an anticipation of David Hume, as when he calls mind “a congeries of perceptions. Take away perceptions,” he adds, “and you take away mind. Put the perceptions and you put the mind. The understanding seemeth not to differ from its perceptions and ideas.” He seems unconscious of the total scepticism which such expressions, when strictly interpreted, are found to involve. But after all, the reader must not apply rigorous rules of interpretation to random entries or provisional memoranda, meant only for private use, by an enthusiastic student who was preparing to produce books. ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ I have followed the manuscript of the _Commonplace Book_, omitting a few repetitions of thought in the same words. Here and there Berkeley’s writing is almost obliterated and difficult to decipher, apparently through accident by water in the course of his travels, when, as he mentions long after in one of his letters, several of his manuscripts were lost and others were injured.