Briefly contrast Descartes's and Spinoza's views on substance, especially on the nature, number, and interaction between substances.

Interaction

The reciprocal action or influence between entities, leading to a dynamic process of exchange or communication.

Descartes's Views

Philosophical opinions of Descartes that emphasize doubt as the basis for certainty and the dualism of mind and body as foundational to understanding existence.

Spinoza's Views

The philosophical perspectives of Baruch Spinoza, which include the monist idea that everything is one substance, often identified with God, and the ethical importance of living a life of rationality and self-control.