Internal Cause and External Cause

A pair of philosophical categories that reveal the fundamental causes and conditions of the development and change of things. Internal cause is the fundamental cause of the development of a thing, and the external cause is the interrelation and mutual effect and influence between a thing and other things. The development of a thing has both internal and external causes.

Mao Zedong said: “The world views of materialist dialectics holds that in order to understand the development of a thing we should study it internally and in its relations with other things; in other words, the development of things should be seen as their internal and necessary self-movement, while each thing in its movement is interrelated with and interacts on the things around it.”

The existence of contradiction has the universality and absoluteness of contradiction. Contradiction is present in the process of development of all things, both sides of which are united and struggling, thus promoting the development of the movement of things. This contradiction within things is the universal cause or universal basis for the movement or development of things.

The changes in nature are due chiefly to the development of the internal contradictions in nature and the changes in society are due chiefly to the development of the internal contradictions in society. Because the fundamental reason of development is in the things themselves and not in other things, development is the “self-movement” of things.

The material world is a whole composed of all kinds of things interrelated. Things are not isolated but interconnected with each other. Nothing can exist separately from the interaction with other things, so the development and change of things have both internal and external causes.

External cause accelerates or delays the development and change of things by influencing their internal contradictions. Thus, the development and change of things are the result of both internal and external causes. But internal and external causes play different roles in the development and change of things.

The fundamental cause of the development of a thing is not external but internal; it lies in the contradictoriness within the thing, and there is internal contradiction in everything, hence its motion and development.

Purely external causes cannot explain why things differ qualitatively in thousands of ways and why one thing changes into another. Even mechanical motion under external force occurs through the internal contradictoriness of things. Mao Zedong said: “Contradictoriness within a thing is the fundamental cause of its development, while its interrelations and interactions with other things are secondary causes.” “External causes are the condition of change and internal causes are the basis of change, and that external causes become operative through internal causes.” "External cause is the condition of change, and internal cause is the basis of change. External cause acts through internal cause.”

Metaphysics denies the theory of materialist dialectics which holds that development arises from the contradictions inside a thing and regards that the motive force of change of things is external. Understanding the dialectical relationship between internal and external causes is of great significance for adhering to materialist dialectics, opposing metaphysics and correctly grasping and dealing with the development and changes of things.