The Essence of the Problem

For Spinoza, the human, consisting of a mind and a body, is not, however, a double being composed of two distinct entities. The mind and body must be thought of as a single unit, not as the conjunction of two extended and thinking substances. In fact, for him ‘the Mind and the Body are one and the same Individual, which is conceived now under the attribute of thought, now under the attribute of Extension.’ Thus Spinoza rules out the possibility of dualism while establishing the possibility of a twofold mental and physical approach to human reality.

But if mind and body constitute one and the same being expressed in two ways, to understand human nature clearly and distinctly we need to understand how these two modes of conception interrelate and come together. The mind (mens), according to Spinoza, is neither a substance nor a receptacle nor a faculty. It is the idea of the body. Therefore, the term mens describes nothing other than the perception or, more precisely, the conception that humans have of their own body – and by extension of the external world – through the various states affecting them. An idea, in fact, is defined as a concept the mind forms because it is a thinking thing. By openly preferring the term ‘conception’ to ‘perception’, Spinoza emphasises the active, dynamic nature of the power of thought operating in the production of ideas. Consequently, the mind is a way of conceptualising the body or forming an idea of it that is more or less adequate, depending on whether the affections modifying it are of a clear or confused nature.

By identifying the mind with the idea of the body, Spinoza provides guidance on how to conceptualise their relationship. He invites the reader to think of their union according to the model of the idea and its object. After establishing in Proposition 13 in Part II of the Ethics that ‘the object of the idea constituting the human Mind is the Body’, he concludes in the Scholium that ‘from these [propositions] we understand not only that the human Mind is united to the Body, but also what should be understood by the union of Mind and Body’.