Frankly, I’m not sure I’ve ever used the phrase on all fours except in its literal sense of ‘on hands and knees,’ but I was vaguely aware that it had a technical/metaphorical meaning, which Orin Kerr explains as follows in a post on the history of the phrase: “One of the legal profession’s stranger expressions is that a case is ‘on all fours’ with another case. It means that the former case raises the same facts and legal principles as the latter and is therefore highly relevant as a precedent.” He cites Michael Quinion’s explanation that “presumably the image is of two animals standing together, both on all four legs, hence in closely similar situations,” but he himself suggests “the visual image is more an animal running alongside the observer than two animals standing next to each other. If an animal is running on all four legs beside you, the thinking might be, it means that it remains close to you and goes where you go.” For much more on the subject, including copious citations, see Mark Liberman’s recent Language Log post, which is where I learned all I know about it.
Another similar phrase: four-square, meaning ‘completely’. As in, ‘I stand four-square behind the proposition’.
One commentator chez Liberman wrote of the use of the expression among philosophers:
one problem was said to be “down on all fours” with another.
I don’t use the expression myself, but I have heard other philosophers in Australia use it – only in the form “A is on all fours with B”, meaning (if I have it right) that A and B are in some salient way congruent, isomorphic, or in accord. Whether or how this fits with the origins of the expression I have no idea.
Interesting to see such uses of the plural fours. Why not He was down on all four looking for a contact lens?
Excitement! I heard “on all fours with” meaning “congruent with” for the very first time this weekend. (From an east-coast lawyer, in a non-business context.)
Myself, I immediately pictured neatly stacked tables. The example of “four-square” slightly ups the chances that the image isn’t completely eccentric.
(Dumb on me — I shoulda read the referenced link first!)
Might have something to do with being steady.
A stand-stay is a very hard thing to teach a dog. Horses are not especially fond of standing still on all four legs. If they’re resting, the’ll cock a hoof, if they’re not, the’ll be moving. Especially if you are trying to look them over…but that’s a WAG.