I Don't Know It's True, but It May Be Possible

In spite of appearances, it is certain that P is relative to the person who says it. And similarly, I can't say something as possible because I don't know it to be false. So in other words, he's trying to get from knowledge and this is a certain stuff. It is certain stuff to the concept of possibility. But we understand I'm just talking about my own level of knowledge, not about the truth of the matter.