This book's aim is to show - as philosophers such as Sartre or Merleau-Ponty believed - that we think with our whole bodies.To the five traditional senses - sight, smell, taste, hearing and touching - Alain Berthoz adds a sixth one : kinesthesia or the sense of movement. We have forgotten it because it is not so obvious, kinesthetic captors are spread throughout the body and not concentrated in one specific organ. An yet, there is a real pleasure in movement, for the one moving and the one witnessing it, just as there is pleasure in the other senses.For there is no movement without thought. We make a decision to walk, to run, to jump or to dance, with the intention of moving from one place to another. We are thus capable of evaluating a distance, programming the trajectory and this with extreme speed, like when we are racing down a ski slope.The sense of movement obliges us to reconsider our conception of the brain. On one hand, it is not a computer that calculates, using information furnished by the senses, but rather a simulator that emits hypotheses on the possibilities of realizing such or such a movement and which then charges the senses with the duty of testing these hypotheses in reality. This is when falls, wrong moves and illusions become possible - when the hypothesis is mistaken. On the other hand, the brain is not a central headquarters that makes decisions and then forces other peripheric organs to execute them : the smallest movement is too complex and often too rapid. The commands for movement are thus decentralized, they are elaborated by the peripheric organs themselves which must execute them using genetically programmed models.Alain Berthoz is a professor at the Collège du France, titular of the Claude Bernard chair and Director of the Neurophysiology of Action laboratory.