By making the nature into material nature it became simple for Descartes to discover the various laws of nature. which became the basis of the development of modern science. However, as Descartes spit the mind away from the nature, man became a reasoning substance and an extended substance at the same time. Although Descartes explained the relationship of two substance, in short, mind and body with the theory of the pineal gland, it never obtained the full satisfaction of people and remained as a problem. The task of Spinoza was to overcome this problem of Descartes, and his solution was rather simple; to bring the mind back to the nature and make the material nature into the nature that comprise both nature and mind. The reason for Descartes to take the mind away from the nature and includes it only to the man is because the free-will of human-spirit was contradictory to the mechanistic naturalism. There was not a problem at all to include the mind into the mechanistic nature since Spinoza denied the free-will by regarding it as the imagination of delusion of human spirit. As a result, he was able to maintain his opinion of one substance that is not separated into mind and substance. And, the substance, according to his view of nature and pantheism, is God. Meanwhile, Leibniz excludes the extension from the simple substance, namely the nomad. He insisted that both Descartes and Spinoza thought the extension as a simple concept that represents the attribute of substance because there was not an attempt of detailed analysis. Thus, as for Leibniz, monad -as a substance- can be defined as a spirit or at least any form that has spirit in it. In this way, Leibniz tried to overcome the problem of dualism by admitting only the variety of non-material substances that has reasoning attribute. This concept of substance had been criticized by the empiricists and, in fact, disintegrated at philosophy. However, the problem of mind and body has been discussed in earnest since Descartes. Also, its active discussion in modern British and American philosophy is originated in Descartes' dualism of substance-attribute. And, as Spinoza's body-mind identity theory has been compared recently with the philosophy of mind in the 20th century, it is suggested as one way to solve the body-mind problem. Deleuze's philosophy, as he admits himself, is affected much from Spinoza's substance-mode theory which views the world as constantly changing. And the 20th century linguistic philosopher Chomsky evaluates Leibniz as the one who grasped the genuine feature of language like himself. Also, there is an evaluation that Leibniz's monadology was the pioneer of Russel's logical atomism. Like this, the view of substance of modern rationalists not only affected the various thought of modern philosophy, but also a repository of modern philosophers' ideological origination.