The body is a mode of the Divine extension. In virtue of the parallelism of attributes and their modes, a natural correspondence exists between mind and body in humankind. At the same time, however, no real interaction exists between them. Mind and body are but two aspects, or expressions, of one underlying Divine Substance. In part 3, Spinoza defines an affect as a modification by which the body's power to act is increased or diminished.
Affects involve both thought and extension.
A natural tendency exists for an individual's passive feelings, or passions, to take control of life and make that individual a slave. The only remedy is to convert passions into actions. In part 5, Spinoza explains how action is achieved. The latter become actions, and humans overcome their bondage. This process is the very perfection of human nature, in which humans intuit their oneness with God.