If you deconstruct yourself entirely – your own reason entirely – you cannot perform, and you cannot reason. Even the idea that one can reason your way out of such a hold doesn’t escape this judgment, since it uses reason to do so. The Kantian idea that only reason can use its own laws to judge itself doesn’t succeed for very long, since “knowing thyself” has to use reason itself to do its own judging.
If someone makes a charge against me and I get to be the jury, the judge, the executioner, the lawyer, and the witness, and I get decide whether I’m guilty or not, then the entire project is biased. The idea the reason can be impartial about itself has no cogency. Why should it be the case, as Kant says, that reason can get us anywhere?
It’s interesting that Kant said almost the same thing, actually, about the Critique of Pure Reason. He said philosophers and scientists will go on using logic, using natural science, using tools of human reason, etc., without ever examining the tools that is used to first understand them, and that is, reason. He said scholasticisms will fill up the libraries, and his impenetrable book will be laying somewhere in a corner proclaiming all of it to be false, and yet no one will understand it, and the indifferentists will never care about it, and human reason will go on just like it has always done. Just like Kant has done himself in the Critique of Pure Reason.
And just like the Greeks who thought they could explain everything in the world, without explaining the human mind and how it perceives anything, or without explaining human language and how it talks about anything, humans have gone on for centuries like naive little lab rats, sniffing and shuffling their way through life. As a Muser said, Kant seems to want to deny reality — but not really.