It would be simple folly, a childish egotism, to pass by in silence the masterly article on this subject in the "North American Review" for October, 1864, and after it to pretend to offer anything new. Whatever the author might have wrought out in his own mental workshop,--and his work was far less able than what is there given,--that article has left nothing to be said. He has therefore been tempted to one of two courses: either to transfer it to these pages, or pass by the subject entirely. Either course may, perhaps, be better than the one finally chosen; which is, while pursuing the order of his own thought, to add a few short extracts therefrom. One possibility encourages him in this, which is, that some persons may see this volume, who have no access to the Review, and to whom, therefore, these pages will be valuable. To save needless repetition, this discussion will presuppose that the reader has turned back and perused the extracts and epitome above alluded to. Upon the very threshold of Sir William Hamilton's statement, one is met by a logical _faux pas_ which is truly amazing. Immediately after the assertion that "the mind can know only the _limited and the conditionally limited_," and in the very sentence in which he denies the possibility of a knowledge of the Infinite and Absolute, _he proceeds to define those words in definite and known terms_! The Infinite he defines as "the unconditionally unlimited," and the Absolute as "the unconditionally limited." Or, to save him, will one say that the defining terms are unknown? So much the worse, then! "The Infinite," an unknown term, may be represented by _x_; and the unconditionally unlimited, a compound unknown term, by _ab_. Now, who has the right to say, either in mathematics or metaphysics, in any philosophy, that _x_=_ab_? Yet such dicta are the basis of "The Philosophy of the Unconditioned." But, one of two suppositions is possible. Either the terms infinite and absolute are known terms and definable, or they are unknown terms and undefinable. Yet, Hamilton says, they are unknown and definable. Which does he mean? If he is held to the former, they are unknown; then all else that he has written about them are batches of meaningless words. If he is held to the latter, they are definable; then are they known, and his system is denied in the assertion of it. Since his words are so contradictory, he must be judged by his deeds; and in these he always assumes that we have a positive knowledge of the infinite and absolute, else he would not have argued the matter; for there can be no argument about nothing. Our analysis of his theory, then, must be conducted upon this hypothesis.