Baruch Spinoza

Spinoza was expelled from the Amsterdam Jewish community at twenty-three, in one of the most savage excommunications on record, for opinions he had not yet even published. He spent the rest of his life grinding lenses for a living (the dust eventually killed him) and writing the most uncompromising metaphysical system in modern philosophy.

His Ethics, published after his death, is laid out like Euclid's Elements: definitions, axioms, propositions, demonstrations. The conclusion: there is exactly one substance, and you can call it either God or Nature. Everything that exists is a mode of this single substance. Mind and body are not two things but two aspects of the same thing seen under different attributes. Free will is an illusion. Salvation is the intellectual love of God — meaning, the understanding of one's own necessary place in the infinite causal order.

He was called the great atheist of his age. He was called the God-intoxicated philosopher. Einstein, Borges, and George Eliot all loved him for the same reasons.