Once your faith, sir, persuades you to believe what your intelligence declares to be absurd, beware lest you likewise sacrifice your reason in the conduct of your life. In days gone by, there were people who said to us: "You believe in incomprehensible, contradictory and impossible things because we have commanded you to; now then, commit unjust acts because we likewise order you to do so." Nothing could be more convincing. Certainly anyone who has the power to make you believe absurdities has the power to make you commit injustices. If you do not use the intelligence with which God endowed your mind to resist believing impossibilities, you will not be able to use the sense of injustice which God planted in your heart to resist a command to do evil. Once a single faculty of your soul has been tyrannized, all the other faculties will submit to the same fate. This has been the cause of all the religious crimes that have flooded the earth. (Translation from Norman Lewis Torrey: Les Philosophes. The Philosophers of the Enlightenment and Modern Democracy. Capricorn Books, 1961, pp. 277-8)

He couldn’t be wrong, basically, yet the doctor had certainly pointed out logical holes in his position. From a logical standpoint the whole world might be a fraud perpetrated on everybody. But logic meant nothing—logic itself was a fraud, starting with unproved assumptions incapable of proving anything. The world is what it is!—And carries its own evidence of trickery.
But does it? What did he have to go on? Could he lay down the line between known facts and everything else and then make a reasonable interpretation of the world, based on facts alone—an interpretation free from complexities of logic and no hidden assumptions of points not certain. Very well—
First fact, himself. He knew himself directly. He existed.
Second facts, the evidence of his “five senses,” everything that he himself saw and heard and smelled and tasted with his physical senses. Subject to their limitations, he must believe his senses. Without them he was entirely solitary, shut up in a locker of bone, blind, deaf, cut off, the only being in the world.
And that was not the case. He knew that he did not invent the information brought to him by his senses. There had to be something else out there, some otherness that produced the things his senses recorded. All philosophies that claimed that the physical world around him did not exist except in his imagination were sheer nonsense.
But beyond that, what? Were there any third facts on which he could rely? No, not at this point. He could not afford to believe anything that he was told, or that he read, or that was implicitly assumed to be true about the world around him. No, he could not believe any of it, for the sum total of what he had been told and read and been taught in school was so contradictory, so senseless, so wildly insane that none of it could be believed unless he personally confirmed it.
Wait a minute—The very telling of these lies, these senseless contradictions, was a fact in itself, known to him directly. To that extent they were data, probably very important data.
The world as it had been shown to him was a piece of unreason, an idiot’s dream. Yet it was on too mammoth a scale to be without some reason. He came wearily back to his original point: Since the world could not be as crazy as it appeared to be it must necessarily have been arranged to appear crazy in order to deceive him as to the truth.
Why have they done it to him? And what was the truth behind the sham? There must be some clue in the deception itself. What thread ran through it all? Well, in the first place he had been given a superabundance of explanations of the world around him, philosophies, religions, “common sense” explanations. Most of them were so clumsy, so obviously inadequate, or meaningless, that they could hardly have expected him to take them seriously. They must have intended them simply as misdirection.