The following work is directed towards its removal. Having, in former publications, called attention to the supposed difficulty, he considers himself bound to avow his present belief that it is imaginary. He has neither the ability to put out of hand a finished composition, nor the wish to make a powerful and moving representation, on the great subject of which he treats. His aim will be answered, if he succeeds in suggesting thoughts, which in God's good time may quietly bear fruit, in the minds of those to whom that subject is new; and which may carry forward inquirers, who have already put themselves on the course. If at times his tone appears positive or peremptory, he hopes this will be imputed to the scientific character of the Work, which requires a distinct statement of principles, and of the arguments which recommend them. He hopes too he shall be excused for his frequent quotations from himself; which are necessary in order to show how he stands at present in relation to various of his former Publications. * * * LITTLEMORE, _October 6, 1845_. POSTSCRIPT. Since the above was written, the Author has joined the Catholic Church. It was his intention and wish to have carried his Volume through the Press before deciding finally on this step. But when he had got some way in the printing, he recognized in himself a conviction of the truth of the conclusion to which the discussion leads, so clear as to supersede further deliberation. Shortly afterwards circumstances gave him the opportunity of acting upon it, and he felt that he had no warrant for refusing to do so. His first act on his conversion was to offer his Work for revision to the proper authorities; but the offer was declined on the ground that it was written and partly printed before he was a Catholic, and that it would come before the reader in a more persuasive form, if he read it as the author wrote it. It is scarcely necessary to add that he now submits every part of the book to the judgment of the Church, with whose doctrine, on the subjects of which he treats, he wishes all his thoughts to be coincident. FOOTNOTES: [ix-1] Records of the Church, xxiv. p. 7. CONTENTS. PART I. DOCTRINAL DEVELOPMENTS VIEWED IN THEMSELVES. PAGE INTRODUCTION 3 CHAPTER I. The Development of Ideas 33 Section 1. The Process of Development in Ideas 33 Section 2. The Kinds of Development in Ideas 41 CHAPTER II.