No, C. S. Lews said something really naïve if not outright stupid: that (some) men (somehow) know what is truth as a matter of fact and that no honest man will disbelieve.
You’re looking at the Lewis quote from the wrong angle entirely.
The meaning of what Lewis said is that honest men will always be driven by their honesty to want to believe what’s true, whether or not they immediately know the truth of it. In fact, sometimes honest men will not be aware that they have failed to believe truth. But their desire to believe truth will drive them to seek to know it.
Lewis did not mean that a man’s honesty can be used as an automatic truth detector.
You know, the thing about a dishonest man is that he always has to go around pretending to be honest. It’s never the other way around.
This goes all the way back to the one whom Alinsky called the original rebel. He’s a liar, but he can’t go around broadcasting that fact. He is forced to pretend to be honest. Alinsky had the same fate. But the honest man never has to go around pretending to be dishonest. Funny how it works, isn’t it?