Thanks for the lengthy reply but I couldn’t find anywhere that you explain in what sense a group of organisms is real. But you’ve used the world real many times in your reply, but only in sentences where you merely assert the group, clade, fish is real. What is it about the clade that makes it real?
I think you’re actually contradicting yourself without having realized it. Particularly where in the previous thread you responded to me like this:
So the clade fish is only recognizable to us now as a distinct clade because a long line of it’s ancestors have gone extinct, leaving us with this illusion that only this particular set of characters seemingly sufficiently different from members outside of the clade, now exist only among members of the clade. Had those ancestors still existed, it would much easier to see how arbitrary it is where you put the line and say “that population right there, that’s objectively the common ancestor of fishes, all it’s decendants belong to the fishes, and all it’s ancestors do not”. Clades, too, are arbitrary distinctions. There isn’t anything that compels us to the clade fish in particular, other than quirks of fossilization and paleontological discovery. That is one of the problems with the old concept of taxonomic rankings into “domains”, “kingdoms”, “phyla” etc.
And I think this is relevant to the previous discussion because it raises the issue of whether we can say that a group of entities sharing certain characters is “real” or not. You have implicitly admitted that we can group things by certain characters and that those groups really do refer to something physically real, even if that realness doesn’t exist at a fundamental physical level.