by Rabbi Avigdor Miller
If we’ll study all the miracles that Hakodosh Boruch Hu preformed in nature, all around us — and these miracles, some of them are stunning! They're staggering in their profundity and complexity — yet the greatest miracle of all is the ability of free will.
Free will is the greatest of all miracles, it’s the most unusual of all things that you’ll see in this universe
It’s against all logic too, since Hakodosh Boruch Hu is “muloi chol ho’orezt kvoidoi ” — Hakodosh Boruch Hu rules over everything, there's nothing that can take place without His express command. That’s a yesoid hayesoidois (fundamental point) of emunah, nobody can lift a finger to harm or help anybody; only Hakodosh Boruch Hu’s will is what takes place in the world. Men can only have free will to choose to do, but to carry out their free will is not in their power.
Now since everything depends on the gezeiras (decree of) Hashem, nothing at all in the universe happens unless Hakodosh Boruch Hu wills it, the question arises... "How is it possible for a man to have freedom to choose between right and wrong, between yes and no.
If Hakodosh Boruch Hu is the One Who controls every kind of change, every kind of motion, every action and every thought, nobody has any power at all, so how can you find such a phenomena as free will in a world which is entirely in the hands of the borei yisborach (Creator)?
And the answer is, we don’t know any answer. It's a nes (miracle). Free will is the greatest of all miracles, it’s the most unusual of all things that you’ll see in this universe. Everything has cause and effect; nothing happens (even nissim) unless there's a certain cause that Hakodosh Boruch Hu set into motion. Whatever happens is the effect of the previous motivations that Hakodosh Boruch Hu created.
But free will is the lone exception... Free will is so important — that’s why mankind is given the ability to feel the urge [for freedom] more than any other urge. We’re in this world to exercise our bechirah. “Uvocharto bachayim” the right to choose, that’s the gift of life. — Free will and the Yetzer Hara (#531)