As I understand it, compatibilism is the name given to the notion that Hard Determinism is true and Libertarian Free Will exists.
At the outset it's clear that you have a fundamental misunderstanding. I'll try to explain.
Libertarian free will (libertarianism) is the notion that free will is logically incompatible with determinism. Its an
incompatibilist position (
Incompatibilism). Incompatibilists are also known as hard determinists.
Compatibilist free will (compatibilism) is the thesis that free will is compatible with determinism. It's a
compatibilist position (
Compatibilism).
Taking these uncontroversial definitions you must see that the quote above makes no sense.
I accept that to be your understanding, and I appreciate why you would have difficulty with my analysis in light of that understanding. I do, however, respectfully submit that your understanding of the meaning of Compatibilism is mistaken -- at least when assessed by the historical debate in philosophy about the concepts we are discussing here.
By way of example, the introductory chapter of the 2003 book "Freedom and Determinism" by Joseph Keim Campbell, Michael O'Rourke, and David Shier," published by M.I.T., explains that there are five schools of thought in this arena -- namely, (i) Compatibilism, (ii) Incompatibilism, (iii) Soft Determinism, (iv) Hard Determinism, and (v) Libertarianism.
"Freedom and Determinism" (like many other respected texts on the subject) uses the term "Determinism" as I have described / defined it above. More specifically:
“Determinism” is a metaphysical paradigm that posits that all activity in the universe is both (i) the effect of all antecedent activity, and (ii) the only activity that can occur given the antecedent activity. That is what is meant by saying that everything is “determined” — it is the inexorable consequence of activity that preceded it. In a deterministic universe, everything that has ever occurred, is occurring, and will occur since the universe came into existence (however that might have occurred) can only occur exactly as it has occurred, is occurring, or will occur, and cannot possibly occur in any different manner.
and
“Free Will” is a philosophical and theological concept that posits that a human being, when presented with more than one course of action, has the freedom or agency to choose between or among the alternatives, and that the state of affairs that exists in the universe immediately prior to the putative exercise of that freedom of choice does not eliminate all but one option and compel the selection of only one of the available options.
As explained in the introductory chapter to "Freedom and Determinism":
1. "Compatibilism" is the name given to the philosophical proposition that (i) it is unknown whether Determinism is true or Free Will exists, and (ii) it is possible for both (x) Determinism to be true and Free Will to exist.
2. "Incompatiblism" is the name given to the philosophical proposition that (i) it is unknown whether Determinism is true or Free Will exists, and (ii) it is not possible for both (x) Determinism to be true and Free Will to exist.
3. "Soft Determinism" is the name given to the philosophical proposition that (i) some form of Determinism is true, and (ii) some form of Free Will exists.
4. "Hard Determinism" is the name given to the philosophical proposition that (i) Determinism is true, and (ii) Free Will does not exist.
5. "Libertarianism" is the name given to the philosophical proposition that (i) Determinism is false, and (ii) Free Will does exist
Using the the five terms defined above, I am an Indeterminist. As I have explained multiple times in multiple posts, I have no view about whether Determinism is a true or false construct or whether Free Will exists, and (ii) I believe that the simultaneous truth of Determinism and the existence Free Will are logically irreconcilable. In that regard, it is important to note that some posters on this board consistently seek to recast my view as being that Determinism is true and Free Will does not exist. That is a false construct by those posters. As defined in "Freedom and Determinism," the view the posters ascribe to me is that of Hard Determinism, and that is not my view because, as I have said multiple times, I have no view on the question of whether Determinism is true or Free Will exists. The only view I have espoused (and done so repeatedly) is that the two concepts are logically irreconcilable.
Despite the fact that some posters on this board insist that they are Compatibilists, they do so without regard to the fact that their repeated description of the components of their beliefs shows that they are Soft Determinists. I say this because the putative Compatibilists on this Board (i) abjectly deny the truth of Determinism as it is defined in philosophy (and for purposes of the definition of Compatibilism), (ii) ascribe to a form of Determinism that leaves room for future alternatives, and (iii) insist they have Free Will of some sort, but not necessarily full Libertarian Free Will. That is textbook "Soft Determinism" and NOT "Compatibilism." And the fact that some folks on this board (even a majority of them) believe otherwise does not change the fact that they are mistaken in their use of the terminology. [And, I am not counting you among them. This is about others.] They are no more Compatibilists than would people who believe in Allah and the teaching of Muhammed be Roman Catholic simply because they call themselves Roman Catholic and then debate other about the teachings of Jesus (which the name they mistakenly give to Muhammed) and argue (wrongly) that Jesus preached about war and violence as a tenet of Catholicism. What they would be is Islamic people who mistakenly believe their religion is called Roman Catholicism, and who further believe that they must be correct in their belief of the proper term for their views because a majority of them are of that view. Another word for such people might be delusional if they were to continue to insist that they are Roman Catholic after learning from the theological scriptures that their beliefs were in fact that of Islam.
Finally, the position you describe as Libertarianism is, according to the definitions I have set forth, actually Indeterminism. As explained in "Determinism and Freedom" (among other places), a Libertarian believed that Free Will does, in fact, exist and that Determinism is a false construct.
Returning to my original answer to your question, and using the various definitions I have provided (which are not my definitions, but the definitions of the philosophical discipline being discussed):
I ascribe to Incompatibilism” because (1) if Determinism is true (i.e., accurately describes the state of the universe), then humans lack Free Will, because both (a) human beings lack the ability to think in a manner that is not 100% caused by prior activity that is outside of their control, as human cognition is simply a form of activity that is governed by the mechanism that makes Determinism true, and (b) there are no such thing as true “options” or “alternatives” because there is one, and only one, activity that can ever occur at any given instant; and (2) If human beings have Free-Will, then Determinism is not true, because both (a) a person with Free Will is capable of thinking in a manner that is not 100% caused by prior activity that is outside such person’s control, and (b) the existence of Free Will depends upon the existence of true “options” or “alternatives” that do not exist if Determinism is true. Again, Incompatibilism does not take a position as to whether Determinism is true or Free Will exists — or neither. Rather, Incompatibilism simply stakes out a position respecting the relationship between Determinism and Free Will, and posits that the two concepts cannot coexist (to the extent that either exists).
Concomitantly, I reject “Compatibilism” as a false construct because its validity depends upon (i) watering down the meaning of Free Will to include the illusion of choice that exists prior to the inexorable occurrence of determined activity that is not and cannot be known until after it occurs, or (ii) watering down Determinism to exclude human cognition from the inexorable path of causation forged through the universe long before human beings came into existence — or by watering down both concepts. Like Incompatibilism, Compatibilism does not take a position as to whether Determinism is true or Free Will exists — or neither. Rather, Compatibilism simply stakes out a position respecting the relationship between Determinism and Free Will, and posits that the two concepts can coexist (to the extent that either or both exist).
The difference between Incompatibilism and Compatibilism is conceptual or ideological and not simply semantic. The law of the excluded middle mandates that only one or the other of these two positions can be true, and that the truth of one of these two positions mandates that the other is false.
“Hard Determinism” and "Libertarianism" both accept Incompatibilism, the difference between them being that (i) "Hard Determinism" also posits that Determinism is true (which logically necessitates a belief that Free Will does not exist), and (ii) "Libertarianism" also posits that Free Will exists (which logically necessitates Determinism is a false costruct).
“Soft Determinism” (which posters on this board confuse with Compatibilism) accepts Compatibilism and also posits both that Causal Determinism is true and that Free Will exists.
As with Incompatibilism and Compatibilism, the difference between Hard Determinism and Soft Determinism is conceptual or ideological and not simply semantic. If Hard Determinism is true, then (i) Soft Determinism is false, (ii) Compatibilism is False, and (iii) Free Will does not exist. If Soft Determinism is true, then (i) Hard Determinism is false, (ii) Incompatibilism is false, and (iii) Causal Determinism is true, and (iv) Free Will exists.
Although there are not names for the positions (or “isms”), it also is possible to believe that (i) Determinism and Free Will are conceptually incompatible, and neither is true or exists, (ii) Determinism and Free Will are conceptually compatible, but only Determinism is true and Free Will does not exist (for reasons other than the truth of Causal Determinism), or (iii) Determinism and Free Will are conceptually compatible, but only Free Will exists and Determinism is false (for reasons other than the existence of Free Will). Perhaps, the first position can be called “Compatibilistic Nihilism,” the second position can be called “Compatibilistic Determinism,” and the third position can be called “Compatibilistic Free Will.”
Again, if I use your definitions, I tend to agree with your views. I would hope that are equally capable of seeing the rationality of the view I have been expressing based on the definitions I am using. Interestingly, in the law, most disputes (especially contract disputes) are the result of disputing parties having a different understanding of the meaning of words they are using in common. In the end, however, one meaning takes precedence over the other, and the meaning that is controlling is the one that is commonly used in the industry in question, and not the mistaken meaning that one party might have based on common parlance or how the words are used in some other context (such as science or physics).