But it doesn't follow that all abstract objects are classes. — Ludwig V

I agree and I don't think I've said or implied otherwise. I'd say abstract objects are probably all generalizations, but I don't think generalization and class are coterminous. That said I'm not confident that on detailed analysis all abstract objects will trun out to be generalizations.

Well, we can agree on that, though we may find complications if we looked more closely at the detail. — Ludwig V

Yes, that seems likely. Analysis always seems to discover complications since linguistic terms are only more or less definitive or determinate. Ambiguities proliferate under the analytic eye.

The difference between that and a symbol would take some teasing out but set that aside. The lack of a convention does suggest that it is not. — Ludwig V

Right, I think conventionality is the key difference between signs which count as symbols and those which do not.

You surprise me. I thought that was what you were suggesting. It's good to know that I was wrong. — Ludwig V

Asking for grounds or justification for your belief, knowledge, actions and perception is not Formal Logic. It is just a rational thinking process for finding out if your beliefs, knowledge, actions or perceptions were rational or irrational.

Right, I think conventionality is the key difference between signs which count as symbols and those which do not. — Janus

So when the goose hisses at me that is a sign (expression) of anger or hostility, which means that I do well to behave cautiously, yet I can only articulate what the sign means by using symbols. Obviously, then, the way I understand what the goose's hiss means, is by means of symbols, which the goose cannot use. Yet the difference in meaning between the two is hard to discern.
Does that make sense? I'm not sure.

Asking for grounds or justification for your belief, knowledge, actions and perception is not Formal Logic. It is just a rational thinking process for finding out if your beliefs, knowledge, actions or perceptions were rational or irrational. — Corvus

Why does it matter whether our beliefs, knowledge, actions or perceptions were rational or irrational? Is it because that is how we know that they are true - or, in the case of actions, justified?
So it seems that even if I believe my perceptions without any grounds, I can justify them - that is, provide reasons (grounds) for believing them - after I come to believe them.

That explanation of why civilizations fall is elegant. Does anyone here disagree with that explanation of why civilizations fall? If we all agree about why civilizations fall, can we use our rationale to prevent that from happening?