Q: You say all is uncertain; but surely my knowledge that I have lived a life is an absolute certainty.
A: We cannot know with certainty that we had a childhood; it may have been programmed into us, or projected into our brains. However, our childhood is a strong appearance to us, and I can't think of anything that would discount it. Therefore, because it is a reasonable idea we should uphold it as a reality.
Q: If we accept childhood because it appears to us, then we should also accept the ego, which is certainly a strong appearance to us. The ego may consist of false thoughts, but it is surely reasonable to accept the conventional reality of the ego, along with all its desires.
A: Hunger is a reality, but we need not put up with it! Likewise, delusion is a reality, but this doesn't mean it has to remain. There are many realities: it is also a reality that I want to live in accordance with Truth, which involves destroying the ego. Childhood may not be a false thought, but the ego certainly is: some things can be known with certainty.
Uncertainty too, is a certainty. Uncertainty does not defeat the purpose of learning, but is the goal of it.