Spinoza discusses the aspects of God’s essence that help explain the human mind.

All things can be classified as extended things or modes of thinking. God is both an extended thing and a thinking thing. Bodies express God’s essence “in a certain and determinate way” (33) in being extended things. As a thinking thing who is infinite, God can “think infinitely many things in infinitely many modes” and “can form the idea of his essence and of all the things which necessarily follow from it” (33). In a manner of speaking, God thinks all things into existence.

Unlike God, man’s existence is not necessary; his essence does not involve existence. In other words, God is a substance, but man is not. Man’s essence reflects God’s, consisting of certain “modes of God’s attributes” (38). The human mind is “part of the infinite intellect of God” (39). So, when we think or perceive, it is God thinking or perceiving through us. However, compared to God, we perceive only “partially, or inadequately” (39).

The first thing the human mind is aware of is the body. This proves that man consists of a mind and a body.