According to Spinoza, what two aspects comprise the single substance?

The correct response is that according to Spinoza, the two aspects that comprise a single substance are Mind and Body. Spinoza posited a form of monism, the belief that there is only one substance in the universe, which can be understood in two ways: as the mental (thought) and the physical (extension). In Spinoza's framework, every mental event has a corresponding physical event, and vice versa, reflecting his idea that the mind and body are two attributes of the one underlying reality.

This perspective also emphasizes the interdependence between mental and physical states, suggesting that they do not exist separately but are two ways of experiencing the same fundamental reality. In other philosophical frameworks, different choices like Thought and Thing might resonate with dualistic interpretations, but Spinoza's framework firmly positions Mind and Body as unified expressions of the same substance.