As for the general answer, we say that your statement, “We do not concede that this proposition is self-evident,” is an inadmissible denial. Self-evident premises cannot legitimately be denied. Were it permissible to deny self-evident truths, neither reasoning nor establishing a proof against someone who denies a claim would be possible. The most anyone advancing an argument can do is present a proof composed of self-evident premises. If such premises could be denied, no argument would be valid.

Likewise, the arguments he has mentioned to show that this proposition is not self-evident, or is not true, are also inadmissible. Self-evident truths are the foundation of truths reached through inference. To challenge self-evident truths by means of inferential truths would therefore be to challenge a foundation by means of something derived from it. This would entail invalidating both the derivative and its foundation. If the derivative is unsound, it cannot legitimately be used as a counterargument; if it is sound, its foundation must also be sound, so it cannot undermine that foundation. Thus, in either case, self-evident truths cannot legitimately be opposed by truths reached through inference.

If it is said: “Granted that self-evident premises may neither be denied nor opposed by inferential arguments, does the mere assertion by someone advancing an argument that a premise is self-evident constitute proof against his interlocutor?”

The answer is: “His mere claim that it is self-evident does not constitute proof against his opponent. But whoever knows that a proposition is self-evident has attained knowledge of it, and he does not deny what he himself knows—whether anyone else knows it or not, and whether anyone else concedes it to him or disputes it. What he knows self-evidently, he cannot doubt.”