Hasdai Crescas חסדאי קרשקש
took Aristotelian physics apart — two centuries before Galileo
Hasdai Crescas was born in Barcelona about 1340 and was the head of Aragonese Jewry. In the massacres of 1391 his only son was killed.
His book — Or Hashem, "The Light of the Lord" — is unusually built. Maimonides and Gersonides proved God's existence and unity relying on Aristotle's physics: the impossibility of a vacuum, the impossibility of the infinite, the finitude of the universe. Crescas went not for the conclusions but for the premises — and showed that not one of them is necessary. A vacuum is thinkable. An infinite magnitude is thinkable. A plurality of worlds is thinkable.
The significance goes beyond Jewish philosophy. Spinoza, in his twelfth letter, refers directly to "a certain Jew named Rabbi Hasdai" and to his argument about actual infinity; through that line Crescas's critique entered European thought on the eve of the scientific revolution.
The second half of the book is on free will and on the bond between man and God being held by love rather than understanding. Here too he objects to Maimonides: the end is not to know but to love.
On the timeline
Sources
Rishonim
- Or Hashem — the dismantling of the Aristotelian premises the proofs rest on
Scholarship
- Spinoza, Letter 12 — the reference to “Rabbi Hasdai” and his argument on infinity
Basis: documents and evidence.