[General] John Stuart Mill expressions

[Brook993]

I have started reading JSM's book to improve my comprehension skills. I have found this sentence a little bit hard to understand. Could you please explain its meaning?
"The subject of this essay is not the so-called Liberty of the Will, so unfortunately opposed to the misnamed doctrine of Philosophical Necessity; but Civil, or Social Liberty ... "

What does he mean by "so unfortunately opposed to the misnamed doctrine of Philosophical Necessity;" ?

 

[GoesStation]

The phrase expresses two ideas: 1) the doctrine called "philosophical necessity" should be described some other way, and 2) another doctrine, "liberty of the will", should not be considered to be an opposing belief.

I've used modern punctuation and capitalization instead of the obsolete system Mill used. Please name the source of quoted texts. The author's name alone is not enough.