What I can imagine and what I cannot -- I can imagine something that I have never seen, or even something that does not exist. But I can imagine anything? Maybe not. For example I cannot imagine a stick that does not have a length. I can imagine a stick length which constantly changes, so that it becomes impossible to measure. But a stick without length, no. And that may be because I have a limited imagination or, rather, because that rod length is not really logically impossible? But Euclid, in the parallel world of geometry, was able to think of a point without dimensions, without a thick line, a circle, surrounding a circle, but which adds nothing to the size of that.