Thread by @EveKeneinan

Understanding the difference between

1 Consensus Gentium
2 Ad Populum
3 Argument to the Best Explanation

This could save you a lot of time and confusion mistaking valid arguments for fallacies.

Consider the example of the King as an argument to the best explanation.

For those of you with Twitter-length attention spans, it goes:

You find yourself in an unknown land. One thing you ask is who rules there. Everyone except one man says they have a king, named Xerxes. The one man who denies this, a filthy man lying in the street, says he is king.

The other people of the land say he’s a madman who thinks he is the king, but Xerxes (they point to a royal palace) is the king.

IS IT AN IRRATIONAL FALLACY TO BELIEVE “This land is ruled by King Xerxes” on the basis of “everyone but one man here says so”?

Obviously not. This is not an “ad populum” fallacy. Given such reasonable premises as “the people who live in a land know who rules it,” the BEST EXPLANATION of everyone’s belief that Xerxes is king, is that Xerxes is king.

It’s a sound argument to the best explanation.

Like inductions, abductions are not 100% necessarily true.

But no one can live by demanding deductive certainty about everything. You don’t KNOW with deductive certainty that most of the things you do every day won’t kill you.

Philosopher Thomas Kelly formulates it thus:

1 Almost everyone believes that P is true.
2 The best explanation why almost everyone believes that P is true, is that P is true.
3 So, P is very probably true.

If you hold abductions to be doubtful, you are going to be helpless when someone starts challenging obviously true things, like human sexual dimorphism.

The claim that there are many or infinite genders seems hard to defeat because (1) people are at a loss as to how to EVEN ANSWER someone who denies that humanity sub-divides into men and women, and (2) this cannot be proven with any kind of formal deductive certainty.

The trouble with demanding DEDUCTIVE CERTAINTY is that you can only HAVE IT in formal systems.

And formal systems have axioms.

And axioms cannot be proven, and so can be disputed.

1 All deductive systems have axioms
2 No axioms can be proven
3 So no deductive system as a whole can itself be deductively proven
4 So if you only accept deductive proof, you’ll have none, since you can’t prove your deductive system via deductive proof

Of course, we’ve known this for 1000s of years. Aristotle says “It is a sign of lack of education” [apaideia] not to know what things it is appropriate to ask for proof of (and what kind of proof) and what not.

An example of the Consensus Gentium:

MOTION OCCURS, or “Some things move.”

Zeno has some powerful arguments that it does not, arguments that remain unrefuted.

Are we irrational to believe “motion occurs”?

Another example of the Consensus Gentium:

MINDS EXIST, or “eliminative materialism is false”

Is it irrational to flatly dismiss someone who argues serious that you have no conscious awareness of anything?

A third example of the Consensus Gentium:

Time has three phases: PAST, PRESENT, FUTURE

In short, to attempt to refute the Consensus Gentium, which includes THE PRIMARY DATA OF HUMAN EXPERIENCE and the EXISTENCE OF PRIMARY HUMAN COGNITIVE CATEGORIES, by calling it an AD POPULUM FALLACY, you cut your own throat, rationally speaking.

If “what, you believe in logic just because everyone else does? That’s an ad populum fallacy!” strikes you as a good argument, get help.