First, think of a straight line.
Second, think of something that can’t cross itself.
But what’s the meaning of the proposition “a straight line can’t cross itself”?
Simple, it just means that there is a group of particulars that you call “straight lines”, that there is a group of particulars that you call “things which can’t cross themselves”, and that each of the particulars in the first group is the same as one of the particulars in the second group. It doesn’t mean anything but that the each of the particular things associated with the first string of words is the same as one of the particular things associated with the second string of words.
For example let’s say that the string of words “straight lines” refers to the particulars A, B, and Y and that the string of words “things which can’t cross themselves” refer to the particulars A, B, C, D, and E. So the proposition that “a straight line can’t cross itself” just points out every particular associated with the first string of words - A, B, and C - is included in the group of particulars associated with the second string of words - A, B, C, D, and E. And, in this example, of course that is true, because, out of the particulars in the first group - A, B, and C - all of them appear in the second group - A, B, C, D, and E. There are two extras in the second group not in the first group, but that doesn’t matter because the proposition just says that the first string of words is “contained in or the same as”, not that it’s necessarily “the same as”.
And, by the way, when I say “particulars”, I’m not just talking about things that appear in the outside world. I’m talking about anything that you can sense, conceive of, or whatever. If you can see it, hear it, or whatever, it’s a particular, whether it’s in your head or in the outside world. Particulars are just things that you can sense or conceive. And, actually, on that note, I should point out that I was asking whether “infinity” in conceivable, acting like it would be nonsense if it’s not. Well, I still have a similar position, but I can weaken it a bit. There’s no reason why I should say that I have to be able to conceive of it - which seems to mean think of it in my head. We could say that infinity is meaningful simply by showing something to our senses, such as moving our finger up and down with no end in sight, or whatever. It doesn’t have to be conceivable, it just has to be something that I could observe - whether in my head or in the outside world. But don’t let that be too misleading. At least in principle - whatever that means - we can conceive of anything that we sense in the outside world. The only problem is that often it’s a lot harder to conceive of something than to just put it in front of us. Let me give you an example. What’s pi? Zang explained it before as imagining something, but I found it pretty hard to imagine. But you could definitely animate it or do it with some plastic or something. Anyway, that’s a bit of a tangent.

