Exploration Through Example

Example-driven development, Agile testing, context-driven testing, Agile programming, Ruby, and other things of interest to Brian Marick

191.8

⇒

167.2

⇒

186.2

183.6

184.0

183.2

184.6

Wed, 25 Feb 2004

William James on differences that make a difference

While I'm on an anti-definition kick, let me quote William James's story of the squirrel:

SOME YEARS AGO, being with a camping party in the mountains, I returned from a solitary ramble to find every one engaged in a ferocious metaphysical dispute. The corpus of the dispute was a squirrel - a live squirrel supposed to be clinging to one side of a tree-trunk; while over against the tree's opposite side a human being was imagined to stand. This human witness tries to get sight of the squirrel by moving rapidly round the tree, but no matter how fast he goes, the squirrel moves as fast in the opposite direction, and always keeps the tree between himself and the man, so that never a glimpse of him is caught. The resultant metaphysical problem now is this: Does the man go round the squirrel or not? He goes round the tree, sure enough, and the squirrel is on the tree; but does he go round the squirrel?

[Stop now and answer the question. When I did, I thought the answer was bleeding obvious. Dawn thought so too, but I was surprised that she thought it was the other answer that was obvious. Since, I've asked others. It's not evenly split, but neither Dawn nor I are alone.]

In the unlimited leisure of the wilderness, discussion had been worn threadbare. Every one had taken sides, and was obstinate; and the numbers on both sides were even. Each side, when I appeared therefore appealed to me to make it a majority. Mindful of the scholastic adage that whenever you meet a contradiction you must make a distinction, I immediately sought and found one, as follows: "Which party is right," I said, "depends on what you practically mean by 'going round' the squirrel. If you mean passing from the north of him to the east, then to the south, then to the west, and then to the north of him again, obviously the man does go round him, for he occupies these successive positions. But if on the contrary you mean being first in front of him, then on the right of him, then behind him, then on his left, and finally in front again, it is quite as obvious that the man fails to go round him, for by the compensating movements the squirrel makes, he keeps his belly turned towards the man all the time, and his back turned away. Make the distinction, and there is no occasion for any farther dispute. You are both right and both wrong according as you conceive the verb 'to go round' in one practical fashion or the other."

That's from his second lecture on Pragmatism (and I'm so glad James died before Mickey Mouse was born, so that I can link to the whole thing).

When I get involved in definitional debates, I often think of James's pragmatic method, which is to ask:

What difference would it practically make to any one if this notion rather than that notion were true? If no practical difference whatever can be traced, then the alternatives mean practically the same thing, and all dispute is idle. Whenever a dispute is serious, we ought to be able to show some practical difference that must follow from one side or the other's being right.

Quite often, there is a practical difference. Then, if I'm lucky, I can focus on which practical difference people want, thus sneaking away from arguing about the definition.

## Posted at 20:07 in category /mangle [permalink] [top]