petitio eleuchi … were they smarter in 1932 than now?


Noni Mausa in comments reminds us:

(We forget)….how essential it is to understand sound and unsound arguments. Arguments are one tool of winning or losing in the struggle against your opponent and his definition of reality — a definition which will effect your life and improve his (or else why would he bother?)

If you get your opponent to accept your definitions. and your terms of discourse, that’s often the first and last move in winning the contest. Structuring an apparent argument out of those is becoming less important, more’s the pity. But the pundits have to do it, or how would they fill out their columns?

In 1932, a Dorothy L. Sayers mystery discussed a point of logic, in among the cut throats and the pursuit of an itinerant barber. It was just a little throwaway paragraph to illustrate how stupid the murderer was.

“…but [Weldon] failed to detect either the petitio eleuchi, the undistributed middle or the inaccurate major premise which it contrived to combine…”

And Bill Peschel, in his handy notations site here: gives definitions:

— petitio eleuchi: begging the question “using as a premise in an argument something that should be the conclusion.”
— undistributed middle: The official definition is “The middle term in the premises of a standard form categorical syllogism never refers to all of the members of the category it describes.”

Granted that Sayers’ readers were smarter than most, still the 1932 reader was perhaps more likely to understand the subtleties of Weldon’s mistake than the modern reader.

This is no minor point — these are not airy-fairy technicalities, they are the nuts and bolts of thought. Not understanding them is as hazardous as not understanding electricity if you happen to be wiring a house.

from comments 1/17/2009 on Robert’s post