"Kant’s expressly stated purpose was to save the morality of self-abnegation and self-sacrifice. He knew that it could not survive without a mystic base—and what it had to be saved from was reason...
"His argument, in essence, ran as follows: man is limited to a consciousness of a specific nature, which perceives by specific means and no others, therefore, his consciousness is not valid; man is blind, because he has eyes—deaf, because he has ears—deluded, because he has a mind—and the things he perceives do not exist, because he perceives them."
“For the New Intellectual,” For the New Intellectual, 30.
How, under that epistemological "principle," can you NOT deny that knowledge is possible?
"From primordial mysticism to this, its climax, the attack on man’s consciousness and particularly on his conceptual faculty has rested on the unchallenged premise that any knowledge acquired by a process of consciousness is necessarily subjective and cannot correspond to the facts of reality, since it is “processed knowledge.”
Introduction to Objectivist Epistemology, 106
"the doubts, the uncertainty, the skepticism that followed, skepticism about man’s ability ever to know anything, were not, in fact, applicable to human consciousness, because it was not a human consciousness that Kant’s robot represented. But philosophers accepted it as such. And while they cried that reason had been invalidated, they did not notice that reason had been pushed off the philosophical scene altogether and that the faculty they were arguing about was not reason.
"No, Kant did not destroy reason; he merely did as thorough a job of undercutting as anyone could ever do."
“Faith and Force: The Destroyers of the Modern World,”
Philosophy: Who Needs It, 64
"Must men then resign themselves to a total skepticism? No, says Kant, there is one means of piercing the barrier between man and existence. Since reason, logic, and science are denied access to reality, the door is now open for men to approach reality by a different, nonrational method. The door is now open to faith. Taking their cue from their needs, men can properly believe (for instance, in God and in an afterlife), even though they cannot prove the truth of their belief . . . . “I have,” writes Kant, “therefore found it necessary to deny knowledge, in order to make room for faith.”
Leonard Peikoff, The Ominous Parallels, 32.