Schopenhauer replaced I Kant's "thing itself" with "will", thinking that will is the foundation and ultimate reality of the whole world, everything is the expression of will, and thought is also the derivative of will. In his view, the world is will and its representation, which can be traced back to reason, but ultimately comes down to will. As the noumenon of the universe, will is a mysterious vitality that is completely hostile to the objective material world, that is, a blind, irrational and never-failing creativity. This will is everywhere and will never die. It is manifested in people's minds as impulse, instinct, effort, desire and demand. Schopenhauer pointed out that the will is the true self and the body is the expression of the will. First I will be born, and then my body and various organs will be born. Even the phototropism of plants and the attraction and repulsion of objects are all manifestations of will. He put reason under the control of will, and thought that will dominated perception, memory, imagination, judgment and reasoning, and human thought and reason should obey mysterious and unexplained will. Voluntarism explains everything in the universe with will, completely denying the objective existence and regularity of nature and human society independent of subjective will, and also denying the possibility of rational thinking to understand the world.
Schopenhauer believes that will is not only the root of all things, but also the root of all evils and pains in the world. Any will must show that it will never be satisfied, so the pain will never end. He suggested that the only way to get happiness is to completely abandon the will to live and be absolutely indifferent in order to get rid of it.
Nietzsche inherited Schopenhauer's voluntarism, abandoned its negative and pessimistic factors, and advocated the "power will theory" of positive action. He gave Schopenhauer a simple will with no purpose and no meaning, and gave life a certain purpose and meaning. This purpose is to yearn for rule and power. He believes that the pursuit and exertion of the will to rule is not only the essence of the universe, but also the only driving force of nature and society, and it is also the highest principle of life and morality. He regards war as the highest realization of the will to power, and thinks that strength is morality.
Nietzsche is an anti-rationalist. He thinks that people's feelings and thoughts are only the expression of will and are dominated by it. All human actions are dominated by will and are activities created by will. In his view, if reason is higher than will, it denies the creativity of will. He also denied that reason can grasp the essence of the world, that is, will.
The voluntarism represented by Schopenhauer and Nietzsche, especially its irrationalism tendency, had a great influence on the philosophy of life history which was popular in Germany, France and other countries at the beginning of the 20th century, especially on H. Bergson's intuitionism, existentialism and pragmatism. It created a trend of thought in modern western philosophy, reflected the demands of modern western liberalism and philosophy of life, and provided the ideological source for deconstructing metaphysics, but it was later misinterpreted by German fascists and became its ideological source, which was once seriously misunderstood.
In modern times, the philosophy of Kant and Fichte also contains the elements of voluntarism. Kant believes that will is independent; Without free will, moral laws are meaningless. Fichte equates will with reason and thinks that will is self and the creator of reality.