Letters 113.16

And among the other reasons for marvelling at the genius of the Divine Creator is, I believe, this,—that amid all this abundance there is no repetition; even seemingly similar things are, on comparison, unlike. God has created all the great number of leaves that we behold: each, however, is stamped with its special pattern. All the many animals: none resembles another in size—always some difference! The Creator has set himself the task of making unlike and unequal things that are different; but all the virtues, as your argument states, are equal. Therefore, they are not living things.

Seneca, Letters to Lucilius 113.16, translated by Richard Mott Gummere