Mind and Body

Although all of Part I of the Ethics is devoted to proving the existence of the one infinite substance, God, this is only done so that Spinoza can proceed to consider the true subject of his work, which is human beings.

In Part II of the Ethics, entitled "Of the Nature and Origin of the Mind", Spinoza moves from the 'macro' level of infinite substance or God itself, which can be considered first under the attribute of extension, and next under the attribute of thought, to the 'mirco' level of human beings. A particular human being is a particular thing, or, a finite mode of substance, which can be considered first under the attribute of extension, i.e. the human body, and next under the attribute of thought, i.e. the idea-of-the-human-body, which is the human mind.

Corollary 2: "It follows that the thing extended and the thing thinking are either attributes of God or affections [modes] of the attributes of God." (p. )

THEORIES OF MIND AND BODY

Here are different possible explanations of the relationship between mind and body:

(1) Causal Interactionism (Descartes)

(2) "Preestablished Harmony" (Leibniz)

(3) Occasionalism (Malebranche)

(4) Dual Aspect Theory (Spinoza)

(5) Materialism (Hobbes)

Spinoza is a Dual Apsect Theorist. Thus, for him, thought and extension, or mind and body for short, are simply two perspectives on the same thing, substance.

"The order and connection of ideas is the same as the order and connection of things." (Bk. II, Prop. 7, p. 180)

"Consequently, thinking substance and extended substance are one and the same substance, comprehended now under this attribute, now under that. So, too, a mode of Extension and the idea of that mode are one and the same thing, expressed in two ways. [...]

And so, whether we conceive Nature under the attribute of Extension or under the attribute of Thought or under any other attribute, we find one and the same order, or one and the same connection of causes -- that is, the same things following one another. [...]

...as long as things are considered as modes of thought, we must explicate the order of the whole of Nature, or the connection of causes, through the attribute of Thought alone; and insofar as things are considered as modes of Extension, again the order of the whole of Nature must be explicated through the attribute of Extension only." (Bk. II, Prop. 7, Scholium; p. 180)

"There we showed that the idea of the body and the body itself – that is, mind and body – are one and the same individual thing, conceived now under the attribute of Thought and now under the attribute of Extension." (Bk. II, Prop. 21, Scholium; p. 189)