In France the _Essai_ is already in its seventh edition. Indeed, one of the most striking facts about Professor Bergson's works is the extent to which they have appealed not only to the professional philosophers, but also to the ordinary cultivated public. The method which he pursues is not the conceptual and abstract method which has been the dominant tradition in philosophy. For him reality is not to be reached by any elaborate construction of thought: it is given in immediate experience as a flux, a continuous process of becoming, to be grasped by intuition, by sympathetic insight. Concepts break up the continuous flow of reality into parts external to one another, they further the interests of language and social life and are useful primarily for practical purposes. But they give us nothing of the life and movement of reality; rather, by substituting for this an artificial reconstruction, a patchwork of dead fragments, they lead to the difficulties which have always beset the intellectualist philosophy, and which on its premises are insoluble. Instead of attempting a solution in the intellectualist sense, Professor Bergson calls upon his readers to put these broken fragments of reality behind them, to immerse themselves in the living stream of things and to find their difficulties swept away in its resistless flow. In the present volume Professor Bergson first deals with the intensity of conscious states. He shows that quantitative differences are applicable only to magnitudes, that is, in the last resort, to space, and that intensity in itself is purely qualitative. Passing then from the consideration of separate conscious states to their multiplicity, he finds that there are two forms of multiplicity: quantitative or discrete multiplicity involves the intuition of space, but the multiplicity of conscious states is wholly qualitative. This unfolding multiplicity constitutes duration, which is a succession without distinction, an interpenetration of elements so heterogeneous that former states can never recur. The idea of a homogeneous and measurable time is shown to be an artificial concept, formed by the intrusion of the idea of space into the realm of pure duration. Indeed, the whole of Professor Bergson's philosophy centres round his conception of _real concrete duration_ and the specific _feeling_ of duration which our consciousness has when it does away with convention and habit and gets back to its natural attitude. At the root of most errors in philosophy he finds a confusion between this _concrete duration_ and the _abstract time_ which mathematics, physics, and even language and common sense, substitute for it. Applying these results to the problem of free will, he shows that the difficulties arise from taking up one's stand _after_ the act has been performed, and applying the conceptual method to it. From the point of view of the living, developing self these difficulties are shown to be illusory, and freedom, though not