This philosophical text deals with the theme of time. A central contention is that science and philosophy alike systematically misrepresent the nature of time. Bergson suggests that the traditional association between the model of space and time is incoherent. Unlike space, time is not measurable by objective standard. This contention is tried out against the major movement in physics of the day - relativity. Tracing the development of the theory from special to general relativity, Bergson finds that a fundamental requirement of the theory is an impossibility - the assumption that the experiences of two observers moving at different speeds within two different physical systems might be thought of as simultaneous. This is to ignore the limits of possible experience.