I think you need to read more carefully. For example, he explicitly anticipates and puts aside some questions you ask: "In this paper, we will not be concerned

I think you need to read more carefully. For example, he explicitly anticipates and puts aside some questions you ask: "In this paper, we will not be concerned with postmodernist critiques of the idea of objective truth nor with skeptical doubts about the possibility of knowledge. I shall assume some broad commonsensical understanding according to which there are truths and we humans sometimes manage to know some of these truths."