If reason is a fallacy, then the question becomes:
What standard is it supposed to have violated?
Well, there is only one standard it could logically violate in order to be proven untrue. And that standard is, of course…itself. Reason must violate reason–rational and logical consistency–in order to be shown untrustworthy.
But how does that work, exactly?
This argument I submit inevitably appeals to the very thing claimed false (reason) in order to prove that it’s false.
?!?!
Okay, let me put it this way. As I figure it, those who want to argue that reason merely affirms itself by being itself, and is therefore tautological, must make their argument by either–
A. Appealing to reason–that is, to logic and rational consistency–as proof that reason is in fact unreasonable.
Or–
B. Appealing to non-reason. That is, asserting that in order to be reasonable–to be rationally consistent and logical–reason must not actually conform to reason. In other words, they must assert that reason, if we wish it to be reasonable (true), must actually be UNreasonable. And so they have essentially surrendered the argument altogether by claiming that what is true is not actually referenced to reason, because they have declared that truth is not a function of reason–of rational consistency and logic. And therefore, if this is the case, then any assertion at all must be accepted as true. Which…makes the assertion that “reason is in fact reasonable and that this is the only way we can really know truth” entirely consistent with their definition of truth and their interpretation of reality. So why are they bothering to argue that it’s not?
Neither A nor B holds any measure of veracity or efficacy for the assertion that reason is false and flawed because it’s a tautological. All it does is reveal that those who look outside of reason for answers to their questions really haven’t yet apprehended the fact that truth needs a reference. In which case, their questions don’t actually make any sense. For example, if you deny that mathematics is of any practical use, and must be untrustworthy because it’s tautological, then there’s no point in asking how far it is to Albuquerque.
Reason, you see, like mathematics, is not a tautology…not a logical flaw. It is, rather, a standard. And this means that its ability to conform to itself is not a failure of itself, but is instead merely proof that it is in fact a good standard.
Stay tuned for part 2!
unreformingtheology 
Adding my two cents: i’m somewhat skeptical of saying that reason as a total category is falseor unreasonable. Indeed it is a situation where there has been that argument that reason is faulty somehow. Quentin miellassoux indicts reason.
But I don’t think this is the alwYs case , I think it always presents for inherent contradiction. I think it’s the incorrect assumption of a common category called reason that stretches out over all of a common humanity is a faulty concept. But that indeed reason is reasonable, and that there is reasoning that does find certain truths.
What we should say is that there are certain philosophical arenas that proposed themselves over a cosmological Stratham called the greater humanity, and this one that likes wise stretches itself to cover this whole cosmological constant has argued itself into a certain net nihilism. As if there’s nothing underneath reason and that there are no qualifiers for what might be true except discourse reason and the like.
This to me locates the faulty concept. But we have failed to qualify what reason is . I’d say it is the assumption that there is a common reasonable or otherwise rational humanity that exist within a unitary arena where in everyone can become educated or intelligent to be able to consider various thought practices or be able to an act certain reasonable procedures is it self the fault of reason.
I think it is more proper to say that a reasoning that has come to a conclusion that there is no substantial basis to objective proposals that is faulty. In other words our current philosophical paradigm again as a general concept is doubly redundant and faulty. To assume that I am speaking in such a way to communicate to a potential of everyone is non sequitur.