Descartes regarded human as a being consisting of the immortal spirit and the body. And he argued that thinking is the property of spirit as extension is that of matter. However, this dualism was not kept thoroughly when he attempted to explain the physiological process of the body. He proposed the pineal gland as the meeting place for spirit and body. La Mettrie, as a materialist, claimed that spirit and body belong to the same material substance. Unlike Descartes, he proposed the automatic movement, sensation, and thinking as the properties of the matter. And he saw no substantial difference between human being and animal, and the foundation of this argument came from the observation of animal and human brains. La Mettrie was a materialist and mechanist, but he was not a reductionist in that he did not think it possible to give a thorough explanation on human physiological phenomena