The forty-six lectures on Metaphysics, and the thirty-five lectures on Logic, published by Messrs Mansel and Veitch, constitute the biennial course actually delivered by Sir W. Hamilton in the Professorial Chair. They ought therefore to be looked at chiefly with reference to the minds of youthful hearers, as preservatives against that mischief forcibly described by Rousseau--'L'inhabitude de penser dans la jeunesse en ôte la capacité pendant le reste de la vie.' Now, in a subject so abstract, obscure, and generally unpalatable, as Logic and Metaphysics, the difficulty which the teacher finds in inspiring interest is extreme. That Sir W. Hamilton overcame such difficulty with remarkable success, is the affirmation of his two editors; and our impression, as readers of his lectures, disposes us to credit them. That Sir W. Hamilton should have done this effectively is in itself sufficient to stamp him as a meritorious professor--as a worthy successor to the chair of Dugald Stewart, whose unrivalled perfection in that department is attested by every one. Many a man who ultimately adopted speculative opinions opposed to Dugald Stewart, received his first impulse and guidance in the path of speculation from the lasting impression made by Stewart's lectures. But though we look at these lectures, as they ought to be looked at, chiefly with a view to the special purpose for which they were destined, we are far from insinuating that they have no other merits, or that they are useless for readers who have already a metaphysical creed of their own. We have found them both instructive and interesting: they go over a large proportion of the field of speculative philosophy, partly from the point of view (not always the same) belonging to the author, partly from that of numerous predecessors whom he cites. We recognize also in Sir W. Hamilton an amount of intellectual independence which seldom accompanies such vast erudition. He recites many different opinions, but he judges them all for himself; and, what is of still greater moment, he constantly gives the reasons for his judgments. To us these reasons are always of more or less value, whether we admit them to be valid or not. Many philosophers present their own doctrine as if it were so much ascertained and acknowledged truth, either intimating, or leading you to suppose, that though erroneous beliefs to the contrary formerly prevailed, these have now become discredited with every one. We do not censure this way of proceeding, but we prefer the manner of Sir W. Hamilton. He always keeps before us divergence and discrepancy of view as the normal condition of reasoned truth or philosophy; the characteristic postulate of which is, that every affirmative and every negative shall have its appropriate reasons clearly and fully enunciated.