What else did the author disagree in the Institutes? Regeneration is through repentance? Bearing our cross? Justified by faith? Prayer is the chief executor of faith? Election? I find that people who like to post such things have never read the Institutes. They simply want to complain about Calvin.
Failure to understand election and predestination is simply to fail to understand God's mercy and grace. As Calvin states:
We shall never be clearly persuaded, as we ought to be, that our salvation flows from the wellspring of God's free mercy until we come to know his eternal election, which illumines God's grace by this contrast: that he does not indiscriminately adop all into the hope of salvation but gives to some what he denies to others." page Chap XXI
If this makes no sense then I would recall that God "hated Esau, but Jacob He loved".
As far as "double predestination" goes, Calvin gives us this warning about such a doctrine in the same chapter:
First, then, let them remember that when they inquire into predestination they are penetrating the sacred precincts of divine wisdom. If anyone with carefree assurance breaks into this place he will not succeed in satisfying his curiosity and he will enter a labyrinth from which he can find no exit. For it is not right for man unrestrainedly to search out things that the Lord has willed to be hid in himself, and to unfold from eternity itself the sublimest wisdom, which he would have us reverebut not understand that through this also he shouldd fill uss with wonder. He has seth by his Word the secrets of his will that he has decided to reveal to us. These he decided to reveal in so far as he foresaw that they would concern us and benefit us."
Predestination and election are important doctrines but Calvin cautions us not to go too deep into this rabbit hole. Why does God love Jacob but hate Esau? How can an impartial God love one but hate another? We can't say but we know that it is true because it is revealed to us in scripture. Calvin only reported the mysteries that are in scripture. Whether one wants to deny those mysteries is entirely up to them.
Isn’t it ironic how Calvin starts the discussion by warning people not to delve into the doctrine of Election too deeply yet he does exactly this in the subsequent pages? When I read this section, I hear him saying that mere mortals should not investigate this issue too deeply yet he (Calvin) is qualified to do just that. In other words, you shouldn’t think about this too much - but allow me to tell you all about it.
Please answer me this question regarding this famous Pauline quote about Jacob and Esau which you just alluded to - who was Paul quoting? And when was this “statement” about Jacob and Esau made?