All choices made by man are not "free". They are determined by God. Calvin clearly denies that it is the "nature" of man that determines him to good or evil. Rather it is according to God's decree that man acts:

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7. They deny that it is ever said in distinct terms, God decreed that Adam should perish by his revolt.503 As if the same God, who is declared in Scripture to do whatsoever he pleases, could have made the noblest of his creatures without any special purpose. They say that, in accordance with free-will, he was to be the architect of his own fortune, that God had decreed nothing but to treat him according to his desert. If this frigid fiction is received, where will be the omnipotence of God, by which, according to his secret counsel on which every thing depends, he rules over all? But whether they will allow it or not, predestination is manifest in Adam’s posterity. It was not owing to nature that they all lost salvation by the fault of one parent. Why should they refuse to admit with regard to one man that which against their will they admit with regard to the whole human race? Why should they in caviling lose their labour? Scripture proclaims that all were, in the person of one, made liable to eternal death. As this cannot be ascribed to nature, it is plain that it is owing to the wonderful counsel of God. It is very absurd 2232in these worthy defenders of the justice of God to strain at a gnat and swallow a camel. I again ask how it is that the fall of Adam involves so many nations with their infant children in eternal death without remedy unless that it so seemed meet to God? Here the most loquacious tongues must be dumb. The decree, I admit, is, dreadful; and yet it is impossible to deny that God foreknew what the end of man was to be before he made him, and foreknew, because he had so ordained by his decree.
Institutes, Book 3. Ch. 23. Section 7.


For "who has known the mind of the LORD that he may instruct Him?" But we have the mind of Christ. (1 Corinthians 2:16 NKJ)