This book is about Gottlob Frege. The guiding thought is that Frege left philosophy a legacy which has been largely ignored, not least of all by his admirers. In order of logical priority, Frege's first concern was to locate the law-like behaviour of truths and falsehoods merely by virtue of their being such (in his terms, the structure of Wahrsein). The just-mentioned legacy lies in his first step towards that goal. It consists in winnowing the 'logical' from the 'psychological', the business of being true as such from that of holding, or holding forth as true-and to keep these separate. A...