What did Epicurus say about whether the universe had a beginning?

Short Answer: Epicurus held that the elements from which the universe is composed are eternal. Although the atoms are constantly in motion and changing positions, such that the things we see now are not permanent, the elements themselves were never created at any point in time by any god or by any other means:

Letter to Herodotus: “To begin with, nothing comes into being out of what is non-existent. For in that case anything would have arisen out of anything, standing as it would in no need of its proper germs. And if that which disappears had been destroyed and become non-existent, everything would have perished, that into which the things were dissolved being non-existent. Moreover, the sum total of things was always such as it is now, and such it will ever remain. For there is nothing into which it can change. For outside the sum of things there is nothing which could enter into it and bring about the change.”

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