How did Benedict de Spinoza’s double-aspect theory describe mind and body?

In the philosophy of mind, Benedict de Spinoza’s double-aspect theory posits that the mental and the material are not distinct, interacting substances, but rather two different attributes or aspects of a single, unitary reality.123

Spinoza identified this single reality as God, or substance, which possesses an infinite number of attributes. Human beings perceive this substance through only two of these attributes: thought and extension (the quality of occupying space). Consequently, individual mental and physical entities are simply "modes" of this one substance.123

Because mind and body are merely different ways of expressing the same underlying events, Spinoza avoided the mind-body dualism that challenged other philosophers like René Descartes. In this framework, there is no causal interaction between mind and body; instead, they are parallel expressions of the same reality. This theory is often categorized as a form of property dualism, as it maintains that mental and physical properties are both present in human beings without requiring them to be separate, interacting entities.234