I am sure the reader will sympathize with me in esteeming it a high privilege to be the humble instrument of ushering into the world so curious a piece of literary autobiography as that which he has just perused. We are here admitted into the confessional. So secret is the communication of thought by the writer to the receiver, that the latter, who was made acquainted with so much of the internal meditations of the former, was not to be allowed to know with what outward man this mind of which he obtained a description was connected. The individual mind was fully and minutely described--to what individual man this mind belonged was to be preserved a profound secret. The writer shrunk from the admission of any man to a participation with him in his self-conferences, and he planned that by keeping his name a secret, the link which would connect this knowledge of the inner to an acquaintance with the outer man should be broken. We have surely in this an argument in favour of the candour and explicitness of his narrative. He felt that to be known, in the ordinary acceptation of the term, by the person he addressed, would be a restraint on the freedom of his revelations--he threw off this restraint, and we are entitled to infer that his letter is a piece of full and candid self-examination. Every word of it, as it was originally written, is here printed, and it will perhaps be admitted that there is not one word of it that does not do honour to its writer. To Aristotle and others it is attributed that they taught esoteric doctrines to a chosen few--doctrines not to be promulgated to the world at large, because they were likely to have a dangerous influence on minds not skilfully trained for their reception. For any vestiges of these hidden doctrines the world searches, anticipating that in them will be found a nearer approach to that which the philosopher believed in his own mind, as distinct from that which he desired to inculcate on others. In all ages there has been a natural and a praiseworthy curiosity to know the hidden thoughts of great teachers. Mankind in general admit, that truth is what is valuable in all philosophy, and if a man entertained thoughts in his own mind in any way different from those which he taught, it has been a conclusion certainly quite legitimate, that truth is more likely to be found in the former than in the latter. But certainly there can hardly be found any other instance in which a document, so likely to be the honest impress of a philosopher's own mind, has been laid before the world; and it is an attestation of the sincerity with which the opinions then in the course of formation in his mind were believed.