Truthiness - Even Older than I thought

In http://sigma5.blogspot.com/2010/10/dumbth-truthiness-and-steve-allen.html I argued that Truthiness is really the same thing as Steve Allen's word "dumbth".  I thought I was doing pretty good to trace the idea that far back until I read "The Greatest Show on Earth" by Richard Dawkins.  It's a great book and you should read it.  But what I am specifically referring to is information I found in his "from the war of nature, from famine and death" section in chapter 13.  The revelation is on page 402 of my copy.

Dawkins refers to a logical fallacy called "Argumentum ad Consequentiam", "Appeal to Consequences" in English.  The concept of a logical fallacy (unreliable argument) dates all the way back to the ancient Greeks.  But according to a paper by Douglas Walton called "Historical Origins of Argumentum ad Consequentiam" published in 1999 in the magazine Argumentation (13 (3) 251-264) this logical fallacy is of more recent vintage.  The phrase was first used in print by James McCosh in 1879.  McCosh was President of the College of New Jersey (now Princeton) at the time.   But this still makes the idea over 200 years old.

An "Argumentum ad Consequentiam" argument goes like this:

• If A is true then something good will happen.
• Therefore, A is true.

There is even a "negative" version:

• If A is true then something bad will happen.
• Therefore, A is false.

In either case good things happen and bad things happen.  They happen whether "A" is true or not.  The actual construction used by the Truthiness crowd is as follows:

• I think it would be a good thing if A were true.
• Therefore, A is true.

I can think of many statements where I think it would be a good thing if they were true.  For instance, wouldn't it be nice if every little girl gets her very own pink Unicorn.  But I know several little girls who don't have and never had a pink Unicorn.  So it is not true that "every little girl gets her very own pink Unicorn".  In a similar vein all the things that the Truthiness crowd believes in because "it would be nice (in their opinion) if they were true" are not necessarily true.  It may be that some of those things are true.  But if so, it is for other reasons.