The main purpose of this book is to elucidate, in a new and original way, this whole question of the logical behaviour of 'know'; but its further and no less important purpose is to show how, once we have grasped the way in which certain key 'know'-statements function, a number of philosophical disputes may be discussed more fruitfully and settled more expeditiously. Some of the analyses offered will be regarded as controversial and will undoubtedly provoke discussion. The style is lucid and economical and technical terms are reduced to a minimum. This work is intended not only for the professional philosopher and the university student, but also for the general reader who is interested in the methods of modern philosophical analysis.