This treatise on Elementary Philosophy, which first appeared in the year 1813, when it procured for me the degree of doctor, afterwards became the substructure for the whole of my system. It cannot, therefore, be allowed to remain out of print, as has been the case, without my knowledge, for the last four years. On the other hand, to send a juvenile work like this once more into the world with all its faults and blemishes, seemed to me unjustifiable. For I am aware that the time cannot be very far off when all correction will be impossible; but with that time the period of my real influence will commence, and this period, I trust, will be a long one, for I firmly rely upon Seneca's promise: "Etiamsi omnibus tecum viventibus silentium livor indixerit; venient qui sine offensa, sine gratia judicent." I have done what I could, therefore, to improve this work of my youth, and, considering the brevity and uncertainty of life, I must even regard it as an especially fortunate circumstance, to have been thus permitted to correct in my sixtieth year what I had written in my twenty-sixth. Nevertheless, while doing this, I meant to deal leniently with my younger self, and to let him discourse, nay, even speak his mind freely, wherever it was possible. But [xviii] wherever he had advanced what was incorrect or superfluous, or had even left out the best part, I have been obliged to interrupt the thread of his discourse. And this has happened often enough; so often, indeed, that some of my readers may perhaps think they hear an old man reading a young man's book aloud, while he frequently lets it drop, in order to indulge in digressions of his own on the same subject.