Question

Good evening.
The Rabbi said in the past (“A Story About 70,” at 8:27; “Head to Head,” at 1:20:18) that nothing is certain, except for this claim.
Afterward, the Rabbi said (in a debate with Yaron Yadan at 1:11:28) that nothing is certain, including this claim.
I would be happy to understand the conclusion.
Let me sharpen the point. I tend to hold by the first statement. Because,

1. The claim that “there is content/truth” is a certain claim, since I am unable to assert anything that escapes a determination of truth. (To claim that “maybe there is no truth” is also a claim.)
2. I then approach classifying contents into the framework of “certainty,” based on 1. (For example, the claim that “affirmation and negation cancel each other out” is a certain claim, since I am unable to assert something—for example, the claim that “affirmation and negation do not cancel each other out,” which cancels out the claim that “they do cancel each other out”—that escapes such cancellation.)
3. When I come to examine content X (in order to classify it), and I try to deny it, and the attempt at denial does not fall into the above failure, then I do not classify it within the framework of “certainty.”
4. If so, the claim that it is not inside the framework is a certain claim (because it is “certain” to me what the framework is).

Now, to claim that “this last claim too is not certain,” meaning that “it is possible that X is in fact certain content,” is actually to claim (/to determine, with certainty) that it is not certain. (That is, at the time and stage of the claim, denying content X does not fall into the above failure.)
A clarification. I am asking:

1. In your words (in the first statement), by “except for this claim,” did you actually mean to claim that the statement “there is truth” is certain content? (That is, that there is something stable.) (A clarification regarding my argument—that “there is certainty/truth”: ostensibly a skeptic would say that “the fact that ‘there is no truth’ is also a claim does not mean that there is truth, and so on and so forth,” and statements of this sort I do not understand.)
2. What is your conclusion regarding these words, and why?

Thanks in advance.