How does Spinoza prove that God is the only independent substance?

Baruch Spinoza, in his philosophical work "Ethics," establishes that God is the only independent substance through his unique metaphysical system. According to Spinoza, there is only one substance in the universe, and that substance is God or Nature.

Spinoza argues that God is a substance with infinite attributes, and two of these attributes, thought and extension, are accessible to human understanding. Unlike traditional monotheistic views, Spinoza's God is not a personal deity but a pantheistic, all-encompassing reality.

In Spinoza's system, everything in existence is a mode or modification of the one infinite substance. Finite things, including individuals and objects, are expressions of the infinite attributes of God. There is no other independent substance apart from God.

Spinoza's demonstration of God as the sole independent substance is rooted in the logical necessity of a singular, infinite reality underlying all existence. The unity of substance eliminates the existence of multiple independent entities, making God the sole and self-sufficient substance in Spinoza's metaphysical framework.