So we are a 2 cat family. This morning I see my wife and son sitting on the couch, watching TV, each with a cat in their laps. I say, “awww, you guys have all the cats!” My know-it-all son, 15 going on 45, says “you can’t say ‘all’ with only 2 of something, it has to be at least 3!” I rejoin, “we have 2 cats, 2 cats are on the couch with you and your mom, therefore, ipso facto, you have ALL the cats!
Please help us settle this grammar / usage crisis; it’s tearing our family apart!
From a usage perspective, the word “both” is generally preferable to “all” when there are only 2 such items in the universe. But this is a general rule of usage, not one of grammar. From a logical perspective, you can use “all” when there is only one such object, or if you really want to be pedantic, zero such objects: “All my sisters have been abducted by aliens, because I don’t have any sisters”. Because of the lack of options for the latter two, I did not vote.
I also think glowacks makes a compelling argument. Perhaps the 15 year-old “not quite” prodigy was misguided or otherwise confused by a similar question over when it is appropriate to apply “several” or “multiple” to a quantity of objects? I would generally think of several or multiple as meaning “three or more.”
ETA: This led me once to ponder whether someone with two million dollars (not me) could properly be called a multi-millionaire or not. And if not, does the “multi” prefix kick in at anything over 2 (like 2.1) or is it limited to integers?
This is not gospel:
1 = one
2 = both
3,4 = a few
5,6 = (I used to have one for this; I don’t remember anymore)
7 = several (“sevenal” would just sound stupid)
8 = I can’t count that high, now
I would not refer to two of something as all. Just three or more.
For example, if I told you all of my friend Jane’s children started the school year on September 7th, would you find that odd if i later revealed she only has two children? I would.
“All,” is, of course, fine for two. And I would argue with your usage, perhaps even preferable, as it emphasizes the inequality of them having everything and you nothing. “Both” would be the more typical usage for two, but there is nothing wrong with “all.” “Both” gives more information, but “all” is more emphatic, perhaps.
The first reply by @glowacks got it right. Logically, “all” can apply to any number of objects, including 0, in which case whatever you say about them must be true.
In case anybody still cares at point, you were completely right and you can ignore all the pedantic attempts to lessen your rightness. IOW, all right - in every sense.