Did John Calvin teach that fallen mankind has free will? The answer to that question might be a little more nuanced than one might suppose, and much depends on how one defines the concept of “free will” in the first place.
One thing at least is certain – Calvin was no fan of the term itself. He writes,
“[I]s it not ludicrous to hang so magnificent a title on so petty a thing? A fine freedom it is, when it is said that man is not compelled to serve sin, but is so much its willing slave that his will is held captive by the bonds of sin! I indeed loathe all quarrels about words, for they needlessly trouble the church. However, I think we should avoid using terms which appear rather absurd, particularly when they risk leading us astray.” (Institutes of the Christian Religion, p.47)
Some might indeed speak of “free will” primarily in order to affirm that sinners sin willingly, rather than by compulsion or against their will. But Calvin clearly held that this was not sufficient warrant to label such a thing as being “free.” He even calls such a term “absurd.”
More than that, as he himself states in the above quote, to use such a term runs the risk of “leading us astray” by causing someone to vainly imagine that “he is master both of his own judgment and his will, so that in his own strength he is able to turn one way or another?” (ibid).
Calvin concludes with the following remark:
“So if anyone would choose to use the word with a proper understanding of what it means, I have no further quarrel with him. But because I believe that it cannot be used without serious risk, and that to do away with it would greatly benefit the church, I would not wish to adopt it myself, and my advice, if it were asked, would be to give it up.” (p.49)
Wise advice. If one needs to explain and qualify a term every time it is used in order to avoid confusion and to prevent people from being led astray, perhaps it is best to simply not use the term at all.