One of the central questions of philosophy is: what is a human being? And this question can be posed in a more personal way: who am I? As we might by now expect, Spinoza's view of the human being challenges commonsense opinions as well as prevailing philosophical and religious ideas. We are probably inclined to think of ourselves as distinct individuals, separate from other beings. Of course, we know that we have relationships to people and objects in the world, but nevertheless we see ourselves as autonomous – a view that is reflected in the widelyheld belief that we have free will. This popular understanding of the human condition is reflected in Cartesian philosophy, which conceives human beings as substances. In fact, Descartes thought that human beings are composed of two distinct substances: a mind and a body.
For Spinoza, however, human beings are not substances, but finite modes. (Last week, I suggested that a mode is something like a wave on the sea, being a dependent, transient part of a far greater whole.) This mode has two aspects, or attributes: extension, or physical embodiment; and thought, or thinking. Crucially, Spinoza denies that there can be any causal or logical relationships across these attributes. Instead, he argues that each attribute constitutes a causal and logical order that fully expresses reality in a certain way. So a human body is a physical organism which expresses the essence of that particular being under the attribute of extension. And a human mind is an intellectual whole that expresses this same essence under the attribute of thinking. . . .