Yes, but an omnipotent God could presumably just make Hitlers not exist. The argument rests on the assumption that there are hidden dependencies in the laws of the universe, such that it was logically necessary that Hitler (or insert whatever other evil here) had to exist to make the best possible world. That's hard to swallow.
Consider that many people today, who live better than the kings of centuries past, are depressed. One could conclude that happiness is a state of improvement over past experiences, not necessarily an absolute scale. If this is true (and I personally believe that it is), then evil is in fact a necessary baseline against which happiness can be improved upon.
This seems to be assuming omnipotence is not just a fantasy?
More likely they were operating under significant constraints…
> an omnipotent ... could
The Architect in Leibniz is not omnipotent, and can only make the best out of what is possible.
Apologies, re-reading this - which is literally false -, in view of a quick re-read of some salient paragraphs:
the Architect in Leibniz is omnipotent, and his project is regarded as the best possible; only, the project involves a limited humanity that cannot understand it.
(In the original writing above I meant 'omnipotent' in an oblique way (including "clarity" and "satisfying all" as "perfections"), which is too stretched and rhetoric not to mislead.)
I think you are just restating what I said. Yes, Leibniz and any of his defenders must assume that there are hidden constraints to what is possible that lie beyond human understanding that made Hitler (just to use a very salient example, but insert whatever evil you like), necessary to achieve a greater good. It is ultimately an argument from faith (just trust in God, he had the best for the world at heart) that can only be accepted by those who already believe.
I meant that it is explicit, not just an assumption but the very metaphysics. A Logos is thought as predominant over the Agent that uses it. (Otherwise, it would be logical to have perfection and only perfection immediately.)
> an argument from faith
I think it remains (it was intended to be) a logical argument from the very definitions (not from devotional faith).
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Edit: sorry, but I realize I misremembered a few important details, that could make the above quite misleading...
Leibniz speaks of full omnipotence. So, that Logos is not "above" Divinity in an ontological sense, but in a purely logical sense. I.e. it was impossible to do differently as this is "the best possible plan", not "the best achievable".
> we are not well enough acquainted with the general harmony of the universe and of the hidden reasons for his conduct; and that makes people recklessly judge that many things could have been improved [... // ...] to know in detail his reasons for ordering the universe as he has, allowing sin, and granting his saving grace in one way rather than another, is beyond the power of a finite mind
~~ Leibniz, Discourse on Metaphysics(1686)