The success of his approach depended crucially on God's benevolence...

The success of his approach depended crucially on God's benevolence: because we can be sure that the divine being would not mislead us, we can trust that our clear and distinct ideas are true. God's character thus forms the basis for our certainty that there is indeed a reality corresponding to our ideas. God's omnipotence entails the ability to do even what is logically impossible. Descartes also regarded God as not merely uncaused, but somehow the cause of himself.

John Locke (1632-1704) held a view reminiscent of scholasticism, that revelation reveals about God what cannot be known by reason alone--yet neither does revelation violate reason. He went beyond the scholastics to affirm that what violates reason cannot be accepted as revelation. His motive was to rule out what he called "enthusiasm," which would include supposed private revelations about God held on the sole authority of an individual's intuition that a revelation is true.

Reason must judge whether a supposed revelation is true. His view further welded the concept of God to reason. Baruch Spinoza (1632-1677) agreed with Descartes that clear and distinct ideas indeed reflect reality, but he thought that philosophy must start with God, not the self. This is because God is first in the order of things. God's primacy is also the reason Spinoza rejected Bacon's method of beginning with observation.

He abandoned his judaistic roots by affirming that God is the whole of reality, and neither transcendent nor personal. Aquinas had concluded that God exists on grounds that the universe needs something outside itself as a cause. But Spinoza believed that there can be only one thing--God--because wholes alone are independent and there can be only one whole (or "substance"). There is nothing outside the whole on which the whole can depend. That whole is a network of truths connected by implication.

That being the case, everything is either necessary or impossible. Since to be free is to be undetermined by anything outside oneself, God is free because nothing can be outside him; and God alone is free because everything within the whole is the way it is by necessity. There is no need to prove the existence of God beyond the need to prove the existence of the one substance. For Spinoza, God is not an external initiating cause of the world and so is not demonstrable as such.

He is nonetheless an immanent and continuing cause of the world.