"Running on All Fours":
I did a bit more research on the use of "on all fours" in legal writing, and my research questions whether Michael Quinion is right when he suggests that the phrase refers to two animals standing next to each other (and thus similiarly situated). When I looked up the earliest uses of the phrase in American decisions, it turned out that they all refer to motion — the cases are running on all fours, or traveling on all fours, or going on all fours.

  Here are the four earliest uses of the phrase in state cases, all in contexts designed to mean "closely analogous":
Snelgrove v. Snelgrove, 4 S.C.Eq. 274, S.C., Jun 1812
"[Another precedent] is that most perfectly like the one now before the court. Indeed it may be said to run on all fours."

Gailey v. Beard, 4 Yeates 546, Pa., 1808
"The case in 2 Stra. 934, runs on all-fours with the present"

Abbott v. Broome, 2 Am.Dec. 187, N.Y.Sup., 1803
"The determination also in Saidler and Craig v. Church, goes on all fours with the present case. The facts were exactly similar."

Hamilton v. Buckwalter, 2 Yeates 389, Pa., 1798
"It is similar to the present case, and may be said to run on all-fours."
  And here are the earliest uses in federal decisions:
Russell v. Wiggin, 21 F.Cas. 68, C.C.D.Mass., May Term 1842
"[A prior precedent] is also an authority to the same purpose; and, indeed, it runs on all fours with the present case."

Bank of the U S v. Goddard, 2 F.Cas. 694, C.C.D.Mass., Oct Term 1829
"The case would seem, therefore, to travel on all-fours with the present."

The William Penn, 6 F.Cas. 781, C.C.D.N.J., Oct Term 1819
"[I]t would have been directly in point, and would have gone on all fours with the present."

Anonymous, 1 F.Cas. 1004, D.Md., 1808
"If this determination does not exactly run on all fours with the case to be decided, its principles are so nearly similar as to render an accurate discrimination very difficult."
  Later cases begin to drop the notion of "running" and just say that the former case "is" on all fours with the latter. This is just speculation, of course, but the context suggests that 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. So if a precedent runs on all fours with your case, it exactly tracks your case. That's my amateurish guess, at least.

Related Posts (on one page):

  1. "Running on All Fours":
  2. The Origin of "On All Fours":
Doesn't it seem much more plausible that "running on all fours" referred to two animals adopting exactly the same gait, rather than just standing there? I suggest this because, well, the term "running" is in the early versions of the phrase, rather than "standing on all fours." In addition in order for two horses or two cases to "run on all fours," they both must be running.
12.20.2006 12:31pm
PatHMV (mail) (www):
I agree with DJR. It seems likely that the idea is that the horses have matched their strides, running essentially as one unit. From the right vantage point, one would only be able to see the legs of the foremost horse; one could see no difference between the two strides.
12.20.2006 12:35pm
Timothy Sandefur (mail) (www):
I had always assumed the phrase "on all fours" referred to the legs of a table--that the table is level if all four legs are the proper length. Otherwise it wobbles. The image would be that if a case isn't exactly right on all corners, it would not be exactly correct as an analogy, but would "wobble" in the logical analysis. I thought this more likely given that nineteenth century lawyers probably often had to deal with wobbly tables.

Obviously this doesn't work given the use of "runs on" or "travels on" all fours. But it makes me think that perhaps it has reference to a carriage with four wheels correctly made? Or all touching the ground at the same time rather than teetering over ruts?
12.20.2006 12:44pm
Martin Grant (mail):
I had always assumed running "on all fours" meant it was a healthy animal and had no defects in anyway, as opposed to an animal that would limp on three.
12.20.2006 1:02pm
Matt L. (mail):
What about an animal that follows in another animal's tracks, matching its track precisely (i.e. with all four legs falling exactly where the first one's legs fell)? Similar to DJR's but the metaphor is tracks, not gaits.
12.20.2006 1:14pm
Rodger Lodger (mail):
Why fourS? Why not four? Ever hear another number referred to as plural, e.g., I broke all threes of the stool legs?
12.20.2006 2:03pm
I'm pretty skeptical that the phrase has anything to do with animals at all. It all seems a little too silly to me.
12.20.2006 3:12pm
Mark A. Perry (mail):
Professor Fowler opines that the legal usage "seems due to a misunderstanding of the earlier but now less familiar metaphorical use by which a theory, tale, plan, &c. was said to run or be o.a.f. when it was consistent with itself or proof against objections or without weak points -- in fact did not limp like a dog on three legs or rock like a table with one leg too short. ... Whether this is or is not its origin, o.a.f. with is now an established idiom." [1952 ed.]
12.20.2006 3:36pm
dantes (mail):
Matt L.'s explanation rings true to me. Certainly better than two dogs standing next to each other . . .
12.20.2006 4:15pm
I have it on good authority that it refers somewhat indelicately to Justice Storey's mistress.
12.20.2006 5:15pm
Mark Liberman (mail) (www):
Earlier citations, from the OED and elsewhere, suggest that the original notion was of a comparison that is (not) lame, in both the literal and metaphorical sense, and that early uses probably had horses in mind.

I've posted some details at Language Log.
12.20.2006 5:19pm
I always thought of it as something dirty. I pictured the two cases being close to each other, but never stopped to think about it. It wasn't until my 2nd year of law school that I noticed my ridiculous thought. From then on, I've always thought it was about trucks, like Optimus Prime. Is that so unreasonable?
12.20.2006 5:48pm
Mark Liberman: Your citations in general ignore the comparative aspect of "running on all fours." The analysis of this quotation seems totally wrong in that regard:

there is not a greater difference between a single-horse chair and madam Pompadour's vis a vis, than betwixt a single amour, and an amour thus nobly doubled, and going upon all four, prancing throughout a grand drama.

The comparison being made is between one of a sort (a single horse chair) and two (a vis-a-vis). Whatever an amour is, if it is "doubled" and prancing about on all fours, I would guess that means that whatever has been doubled is also prancing about in concert.

Thus "on all fours" seems to have meant not running soundly but two things acting as one.
12.20.2006 6:11pm
Dave Long (mail):
Logic is good, but in this case empiricism works better. Instead of guessing, ask someone who keeps working animals how to spot a lame one.

DJR: the reason for "running" is that a less serious injury may not affect how an animal stands, but it will certainly affect both how it runs and its ability to work. The parse is "(goes on all fours) with", not "goes (on all fours with)".
12.20.2006 8:38pm