“God, or a substance consisting of infinite attributes, each of which expresses eternal and infinite essence, necessarily exists.” 

Spinoza sets out to prove that God exists, on the basis that such a being must necessarily exist. His argument rests on God’s attributes of infinity and perfection. Because humans, as finite beings, exist, it necessarily follows that an infinite being exists who is the cause of us. As Spinoza puts it, “either nothing exists or an absolutely infinite Being also exists” (8).

“Whatever is, is in God, and nothing can be or be conceived without God.” 

This quote relates to what is often described as Spinoza’s monism (all reality is one) and pantheism (God is in all things). Everything that exists is in some sense in God. This is because God is the one and only substance from which everything else derives. Only God is the cause of his own being; all other things come from him.

“In nature there is nothing contingent, but all things have been determined from the necessity of the divine nature to exist and produce an effect in a certain way.”

This is clear statement of determinism, or the theory that all facts and events are the result of natural laws. Things are the way they are because of God’s eternal nature, not because God deliberately chose to make things a certain way. The same goes for human actions; we may imagine that we are acting out of free will, but in fact we are reacting to affections and emotions that come from the laws of nature.