malgxoj: "leono estas besto" and "besto estas leono" are in fact intended to be equivalent statements, although of course the first is more normal than the second.

I would say that the 'reversed' usage, which Harlow admits is unusual, is poetical, and might work with that particular example because the meaning is obvious. However I would not recommend its use too freely. As Harlow says, "you have to use non-grammatical knowledge to determine which is the individual and which the group".

Also, as Wells says in Lingvistikaj aspektoj de Esperanto:

Se A estas B, do ankaŭ B estas A. Tamen necesas konfesi, ke esti povas indiki ankaŭ tiun rilaton, kiu estas ne identeco sed la aparteno al intersekcantaj aŭ inkluzivitaj ensembloj (aroj). Diri, ke leono estas besto ne nepre estas la sama afero, kiel diri, ke besto estas leono.

I translate: "If A is B, then B is A as well. But we must admit that "to be" can also indicate the relation which is not identity but membership of overlapping or included ensembles (sets). To say, that a lion is an animal is not necessarily the same thing as to say that an animal is a lion."

The asymmetric meaning of "is" (or ESTI) is sometimes called the "is of predication," in philosophy, at least.

Socrates is wise = Socrates is a member of the set of wise beings.

A dog is an animal = Each member of the set of dogs is also a member of the set of animals.

The so-called "is of identity" is completely different. And it's symmetric; the order of elements doesn't matter.

"Clark Kent is Superman" = The invidual named Clark Kent and the individual named Superman are one and the same.

I don't know why we use "is", or ESTI, for both jobs, or if there are languages that don't.

FWIW, Spanish also uses the same verb ("ser") for both meanings.

Regards,

Daniel

T0dd:The asymmetric meaning of "is" (or ESTI) is sometimes called the "is of predication," in philosophy, at least.

Socrates is wise = Socrates is a member of the set of wise beings.

A dog is an animal = Each member of the set of dogs is also a member of the set of animals.

The so-called "is of identity" is completely different. And it's symmetric; the order of elements doesn't matter.

"Clark Kent is Superman" = The invidual named Clark Kent and the individual named Superman are one and the same.

I don't know why we use "is", or ESTI, for both jobs, or if there are languages that don't.