Bonus Extra Post. Everything You Wanted to Know About Ipsedixitisms (But were afraid to ask.)

I decided to explain more about "ipse dixit logic" (talk about a contradiction) as that phrase is not exactly part of the common vernacular. I likely first learned the expression sometime before starting law school, but can't say if it was during my undergrad years, or even before that. Nonetheless, thanks to the fine folk at Wikipedia, I can provide some more explanation of this phrase that, in the snotty old Latin, describes one of the most overused forms of fallacious argument.


Ipsedixitism

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Ipsedixitism is the pejorative term for an unsupported rhetorical assertion; the term in Logic for a missing argument.

An ipsedixitism is not explicitly defined as an axiom, and certainly not as a "premise", but often appears as such in a syllogism like: "The economy needs more scientists, so expansion of science education will boost the future economy". The proposition rests on an ipsedixitism unless reasons are given that the "economy needs more scientists".

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Typical causes of ipsedixitisms

The ipsedixitism is a self-referential Appeal to authority. As in:
"Trust me..."

Without reasoning or citations, the first sentence in this definition would be an 'ipsedixitsm'.
A naïve ipsedixitism is not intentional, such as:
The ipsedixitism is an implicit assumption, accidentally made explicit.
The ipsedixitism presumes general agreement, as in a homily.
The ipsedixitism is unstated dogma, or believed to be a matter of fact, e.g: "As a human carcinogen, DDT must be banned worldwide."

The ipsedixitism is a stubbornly unsupported repetition of a disputed claim, asserting the user's power1 or disinterest in objections.

The ipsedixitism is a deliberate sophistry, attempting to smuggle assertions into an argument.

Ipsedixitisms are given as though absolutely no supporting argument is necessary. One motivation for not supporting declarations is the hope that it will make the declaration less visible, particularly in an obfuscated chain of mathematical or legal reasoning. For instance, the 1998 Indiana tax court held that a particular 'formula' for rejecting tax adjustment appeals was the "apotheosis of ipsedixitism", because no evidence was presented that this 'formula' reliably converted tax assessors' criteria into the conditions necessary for appeal rejection (the connection had simply been stated as a bald ipsedixitism in an obscure tax code sub-section).

http://en.wikipedia.org/wiki/Ipsedixitism

There it is, in something slightly larger than a nutshell. As usual, there is more if you follow the link. Oh. I particularly enjoyed the inclusion of the following link, in the Wikipedia article:

See also
Humpty Dumpty