I've been looking at Skepticism, following Maddy's 2017, because it connects with the topic of this month's posts: so what if logic gives us paradox? Even highly evolved apes are unlikely to have a perfect logic. We see a tree, we know that it is a tree; that much is ordinary. We cannot rule out its being an alien quasi-stick-insect, but we never thought that we should; and now that we think about it, perhaps we could if we examined the tree more closely. Of course, we cannot ever rule out that it's an alien quasi-stick-insect of a very convincing kind, by the very definition of that kind. And were it such, it would not be a tree ... but still: so what? Nowadays we have formal logics, and modern theories of truth, much as the earliest scientists stopped relying on intuitions about geometry. What is the truth about truth? The first "truth" in that question is clearly intended to be correspondence truth, but if it does turn out to be the case that the second one cannot be correspondence, then how could the first one be? And if the first "truth" is not correspondence truth, then how satisfying could any answer to any such question be? If we have, for example, an attractive story about how truth is an attractive story, then so what? But still, we do assume that truth is correspondence truth. Even when we think about the formalities, our meta-logic is simply logic. And similarly, we simply assume that trees are not alien quasi-stick-insects of some very convincing kind. We can say that they are very probably not aliens, and then try to justify that "very probably;" and then wonder why we are doing all of that. At the end of the day, we are simply such that, for us, our logic is necessary. I see a tree, and know that it is a tree. I cannot rule out its being an alien quasi-stick-insect of a very convincing kind, and so my "know" is a sort of gamble: I assume that it isn't an alien. I don't know that it's unlikely to be one (how could I?) but I do know that it's not mad to assume that it isn't one. Since the topic is raised, I admit that it might be an alien, that I don't know that it isn't, that I don't know, in that sense, that it is a tree; but I still claim that I do know that it is a tree, in the ordinary sense. There do seem to be at least two senses of "know" in play.