Bergson’s principal aim is to direct our attention to the reality which he believes we all actually know already, but misinterpret and disregard because we are biassed by preconceived ideas. To do this Bergson has to offer some description of what this reality is, and this description will be intelligible only if we are willing and able to make a profound change in our attitude, to lay aside the old assumptions which underlie our every day common sense point of view and adopt, at least for the time being, the assumptions from which Bergson sets out. This book begins with an attempt to give as precise an account as possible of the old assumptions which we must discard and the new ones which we must adopt in order to understand Bergson’s description of reality. To make the complete reversal of our ordinary mental habits needed, for understanding what Bergson has to say requires a very considerable effort from anyone, but the feat is perhaps most difficult of all for those who have carefully trained themselves in habits of rigorous logical criticism. In attempting to describe what we actually know in the abstract logical terms which are the only means of intercommunication that human beings possess, Bergson is driven into perpetual self-contradiction, indeed, paradoxical though it may sound, unless he contradicted himself his description could not be a true one. It is easier for the ordinary reader to pass over the self contradictions, hardly even being aware of them, and grasp the underlying meaning: the trained logician is at once pulled up by the nonsensical form of the description and the meaning is lost in a welter of conflicting words. This, I think, is the real reason why some of the most brilliant intellectual thinkers have been able to make nothing of Bergson s philosophy: baffled by the self-contradictions into which he is necessarily driven in the attempt to convey his meaning they have hastily assumed that Bergson had no meaning to convey. The object of this book is to set out the relation between explanations and the actual facts which we want to explain and thereby to show exactly why Bergson _must_ use self-contradictory terms if the explanation of reality which he offers is to be a true one.