About his erudition there cannot well be two opinions among those who have had opportunities and competency for judging. Its mere mats was a thing extraordinary: it was minutely exact in all those points ebich raise the question of accurate scholarship : it spread over tracts of rssuling the most obscure and neglected : and it was, everywhere, the real knowledge of a thinking man, not the word-cramming of a pedant. His range embraced all the great divisions of knowledge, except mathematics and physical science ; while here too it did not 'elude anatomy, with physiology and some other branches of medicine. Ile was a thorough linguist in the classical tongues, and in German. With as little as possible of the poetics] temperament, he was well read in the great poets; and his historical information was unusually extensive. In philosophy, he was familiar with the Greek writers one and all : Aristotle and his commentators he had probably studied more extensively and profoundly than any even of our Teutonio neighbours. He knew the whole course of the scholastic philosophy, ?s no man else has ever known it since the middle ages departed. With British systems it is needless to say that he was familiar in all directions ; and he was the only man among us who came near to having studied—and nowhere either carelessly or at second-hand—all the German systems that have emerged or diverged from that of Kant.
On the other hand, this question may be put : not whether Hamilton was the most original of philosophers; but whether there has ever been any philosopher who, to learning even half es great as his, united eo much of real and active originality as a thinker. In his treatment of details he has a favourite manner, which often disguises his independence. Ho likes the position of an interpreter: he is wont to speak as if the best way of discovering philosophical truths were by decypberieg them in some mediroval text through the dust of centuries. He takes a pride in quietly fathering, on some schoolman or other, a doctrine or an argument which many men would have been too glad to take credit for as their own ; and sometimes, half-hidden in a brief note, there is given, as an obvious and matter-of-course comment on a scholastic brocard or term, some assertion which proves on close inspection to presuppose a wide process of new inference. The outlines, however, of those sections in his own philosophical creed which he has taken the trouble to expound, are laid down broadly enough to let their character be seen clearly. Be his leading doctrines held true or false, valuable or worthless, they are at least his own,— as much his own as very many systems which all of us rightly admit to be essentially novel,—as much his own, it may be said, as any system of philosophical opinions can be, unless it ignores everything that great thinkers have ever thought before.
What may be the correctness, and what the value, of his peculiar opinions, is a question on which, if it were to be adjudged at present, contradictory verdicts would be given. Probably no one will be competent to decide it justly, till there has taken place a long and intelligent sifting of speculations, which travel in a track, nut only at several points new in itself, but likewise, everywhere, little familiar to most thinkers in this country. Hamilton's writings aro Germanic rather than British ; and that not merely in the freedom with which he has taken German doctrines and methods (with a large admixture of Scholasticism) as materiels to be distilled in his own alembic. The
exotic character is observable, both in his highly speculative aims, end in his severe exactness of technical expression. The former of these characteristics is distinctively alien to the broadly practical English mind ; and the latter is one which has never, before him at least, been made to take root in the philosophic mind of Scotland. Nor can his writings be mastered without pains. He never cares for doing more than saying what he thinks to be worth saying—saying it unequivocally, and saying it in the smallest number of words that I. consistent with safety. He will not turn aside to amuse us ; he will not hurry or rise to excite us. lie is a bard thinker, and a hard, vigorous, precise, dry, writer. But for such as will take the trouble to follow his course of thought, and reflect on its contents, there are perhaps no philosophical discussions, certainly none of our times, that are so suggestive of processes of thought—processes wide in range, defluito in direction, ?nd lofty in &wig° and io possible result.
Of Hamilton's Psychological and Metaphysical doctrines, nothing special requires to be said. They are before us, in certain parts, in his own exposition ; and that they have already been much discussed, and have in some quarters excited a powerful influence on speculation, is a good omen for philosophy. We have, especially, his treatment of three great problems in philosophy. First, there is his theory of the two kinds of human knowledge, Immediate and Mediate. Secondly, there is a special application of thle theory to the construction of a theory of External Perception. Thirdly, there is an exhaustive system of Metaphysics Proper, or Ontology, in his ' Philosophy of the Con ditioned,' or 'Conditions of tho Thinkable '—a vast and noble idea, traced out for us, as yet, in nothing but a tantalising fragment.
Regarding his Logical system, our publio information is still very unsatisfactory. It is to bo gathered from an appendix to his ' Dis cussions,' and an authorised but meagre publication from teatimes, Paynea's ' Now Analytic.' These materials will probably convey no distinct notion of the system, unless to readers who are familiar with the German methods of logical analysis since Kant. The leading points may bo said to be four ; and it is perhaps possible to make these intelligible, very briefly, to persona acquainted with the outlines of the science in ite received forms. 1. H anilton insists on having, in all propositions through common terms which aro set forth fur logical scrutiny, a Pim of quantity prefixed to predicate as well as to subject. The point, though merely one of form, is curiously suggestive of difli culties, and hence of solutions. 2. Instead of recognising only four forms of propositions, the A, H, I, 0, of the old logioiane, he insists on admitting all the eight forms which are possible. (See Thomson and Sully.) 3. lie widens the range of the syllogism, by admitting all moods which can validly bo constructed by any combination of any of his eight kinds of propositions. 4. The Port-Royal doctrine, of the inverse ratio of the extension and comprehousion of terms, ie worked out by him in its reference to the syllogism. This application of the doctrine has certainly not been anticipated by any logician ; and, when elaborated to its results, it throws many new lights on the character and mutual relations of the syllogistic figures.