What does Athens have to do with Jerusalem?
I think this is the question at bottom for twenty first century philosophy. At the beginning of the twentieth century G.E. Moore and Bertrand Russell, on most accounts, rebelled against German Idealism, then the most influential school of philosophy in the U.K., Europe in general, and the United States. They believed that the Idealist argument failed to provide an adequate response to the skeptic. Yes, according to the Idealist, things did not really exist. Moore and Russell worked hard to come up with an argument that did better at demonstrating what they thought was obvious, that, in fact, Moore, for example, could know that he had hands. The solution they came up with came to be called "analytic" philosophy.
George Edward Moore
On my view, you can't ignore Wittgenstein as the preeminent philosophers of the twentieth century. He understood that the problem for 20th century philosophy and its predecessors was the claim that reason has been understood as a matter of logical argument, and if it is so understood, then language, and all of the other issues important to philosophers, is impossible. Twentieth century philosophy was, at bottom, a working out of how both of his proposed solutions. His solutions were suggested in the Tractatus Logico Philosophicus, where he focused on language being a map or picture of reality, and the Philosophical Investigations, where he proposed the idea that the distinctions embodied in language showed that the skeptic could not be correct about language, knowledge, or morality being impossible.
Both solutions proposed by Wittgenstein fail because they do not go any farther than the proposals already put forth by Plato and Aristotle whop tried to respond to what Socrates had put forth. When Socrates claimed that our lives are like the lives of his cave dwellers, neither Plato nor Aristotle rejected that analogy. They instead accepted this claim and proceeded to try to show how we as cave dwellers go on to have language, knowledge, and morality. Aristotle and his followers argued that our lives consist of nothing more than what we experience within the cave. We can have no evidence that there is anything outside the cave. Plato and his followers argue that nothing can be proved by merely making correspondences between words and things in the cave, one has to point out that we can make distinctions between real things and mere copies or shadows of things, and that this is a more adequate response to the skeptic.
Twentieth Century analytic philosophy claimed that the terms of logical arguments corresponded with the things that actually existed in the world and that it was this correspondence that gave them their meaning. It was the fact that logical arguments had meaning that there actually was knowledge and morality. Wittgenstein realized that any such argument cannot answer the skeptic because such an account makes language "private." That is, if language is "private" in his sense, then it is not possible. He supposed, at some point, that if one argument made language "private" and fail at responding to the skeptic, then another argument that made language out to be "public" might succeed at responding to the skeptic. This "public" version involved arguments about language games and their rules which can be publicly observed.
I suspect that Wittgenstein would have come to see that the account provided in his Investigations also fails. The fact that one can make a distinction between, say, a reasonably accurate account of what a word means involving an example of ordinary discourse, using all of its relevant details, and a mistaken account of meaning relying on a misunderstanding of the same example, does not mean that one can have a language, knowledge, or morality, given one is initially committed to one's reason being a matter of logical argument. You can't get there from here, so to speak. He had already understood that an account of logical argument involving correspondence between their terms and the world cannot work. Just because you can make correspondences between a term and a thing does not imply that you have a language, knowledge, or morality if you start out supposing reason is a matter of the logical kind of argument.
What then should we be doing in order to adequately answer the skeptic and to quit repeating the failed responses of the past? John Cook says the best procedure is to put the question marks down far enough and I agree with him about that. Unfortunately, he did not put his own question marks down as far as they need to be put in order to get beyond the positions of Aristotle and Plato. Cook saw only that by rejecting empiricism he was getting at his own bugaboo. He failed to see that rationalists also get their strength from rejecting the empiricist nostrums. He did not adequately see what it would take to reject not only empiricist but also rationalist approaches.
I'm saying we have to look at what Socrates argued to make it seem acceptable that our lives should resemble in any way the lives of his cave dwellers. It is the cave and the fires which provide the battleground upon which both the empiricists and rationalists have fought.
Socrates is clear that language, knowledge and morality is something we will understand if we examine and understand the workings of his Allegory. At first, he thinks the Guardians can be educated enough to themselves climb out of the cave, see the outside involving the fires and the forms, and then rule in light of that knowledge. It becomes clear, however, that there will be endless dispute about whatever the guardians claim about the forms. Another argument is made claiming that there would be those who could enter the cave from outside, unfettered by the prejudices of those in the cave, who would be able to give an unvarnished, metaphysically free, account of the forms and the cave dweller's reality. This is the story of the "Socratic Hero," as I've put it.
In order to reject any one part of this nest of suppositions, one has to be able to do away with them all.
How can this be done? We must determine how one supposes that reason is a matter of logical argument.
First of all, one can determine that there are alternative accounts of argument. Where logical argument is a matter of claim and its support, argument itself is a matter of controversy, a claim about that controversy, and support for that claim.
Second, one has to determine why one would be persuaded for the one and not the other. That is, what is the controversy about which these arguments are made? The most likely controversy has to do with Abraham. Is he tempted by the voice that tells him to slit the throat of his first born, or is he persuaded by the voice that tells him it's not the time or place to slit throats, or anything else of the sort.
Third, we would have to determine what would make one choose the throat slitting over the persuasion. I have thought the most likely and strongest argument has to do with the question one should have about the ends and means of life. One might think that the purpose of life is to survive. There is nothing else more important because without survival, nothing else can be accomplished. One has to think, not only must one survive, but one must exist on a battlefield where the way to survive is through the use of force, i.e., violence, stealth, and deception. This is what, I suppose, makes the slit your throat voice attractive.
The alternative has to do with the claim that the purpose of life has to do with resolving conflict. In order to resolve conflict one has to rely not on force, but on words and the arguments one can make with them.
To sum up. there is an argument taking place between the sons of light and the sons of darkness. The sons of darkness argue that Abraham cannot make decisions on his own about the authenticity of claims about God. He has to accept that if some voice out of a rock says to kill his first born, he has to do so in order to show his piety. This leads to the idea that reason, our human nature, involves such blind obedience to the powers-that-be. Socrates makes the argument that it is only reasonable and right to accept such a view of ourselves. There are certain problems with this view, unfortunately. They include, if we do commit ourselves to such a position, the impossibility of language, knowledge, morality, justice, love, and everything that we might care about. The terms of what arguments we are left with, for example, logical arguments, are determined by the powerful. This is a view suggested by Thrasymachus, but subtly opposed by Socrates. Life for we who live under these commitments becomes not worth living. Since such a position would be rejected by any reasonable person, for example, the Athenians, Socrates argues that there is some excuse for such a predicament, that is, our objections are based on our only seeming to have lives. He argues, our lives are really like those of the cave dwellers. The reward for going along with the slit the kid's throat request, is that we'd have a powerful deity on our side and life after death. It's a kind of extortion.
In other words, Athens and Jerusalem are pretty much the same place. If we want to understand how to object to the empiricists and the rationalists, we have to see that there is an argument that unifies philosophy and Abrahamic religion on the questions at the root of them both.
Lots of wild and crazy claims. But, the first task is to get a picture of all that's involved. Then we try to prove it.