Bayesian argument to believe in aliens?

obiwanbenobi

Active Member
why is it that all of the UFO's we see are close up and never seen further out into space? there's all sorts of telescopes being pointed "Out There[tm]" but do we ever see unusual zig-zag motions in space or flying saucer shaped asteroids? no.

all the local phenomena in the world are likely to be either man-made or natural things that some perhaps have not been explained yet, but by no means are they exhibiting anything i'd consider alien.

i have, by number, many more billions of examples of people being nutty.
 

johne1618

Active Member
Now are you sure you really want to throw the "supernatural" into the mix?

I see you define it as "The supernatural cases could consist of any phenomena that can’t be explained by our current understanding of science." Would that mean that thunder was supernatural until the causes were discovered and suddenly became natural after that point? No, it was merely natural but not yet understood.

Instead of generalizing the argument by using the terms “supernatural” and “natural” I should have used the terms “unexplainable” (by current science) and “explainable” (by current science).
 
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Mendel

Senior Member.
Yes. Zeus throwing down lightning from the Olymp used to be a thing.
I should probably explain that a bit more.

In ancient Greece, lightning wasn't "unexplained". The explanation was that the gods caused this.

"natural" means that something occurs by itself, without human intervention.
"artificial" means human intent has a hand in it.

If you hear something funny that makes you laugh, it's a natural reaction. If your boss cracks a "joke", your laugh may be artificial. Food that grew by itself is "natural", food ingredients created by humans in a chemical factory are artificial.

Now if we have an explanation that involves intent, but no humans, it's neither natural nor artificial, but supernatural: gods, aliens or ghosts causing stuff to happen is supernatural.

A similar division is between the physical world and the spiritual word: thoughts are not things. The physical world is sometimes called the "natural world". Phenomena that go beyond the physical world are then supernatural, and that would include ghosts, gods, and psychic powers, but not extraterrestrials, unless these ETs used psychic powers to travel here and hide themselves.

I think that's where we can connect to the "what evidence" thread: evidence of aliens is not acceptable if it requires us to believe the aliens have supernatural powers; and "breaks the known laws of physics" is just code for that.

I have great confidence in the laws of physics. I couldn't rate any witness report as "90% certain" that involves violating a physical law. @johne1618 's bayesian argument fails on this, and arguments of the type "this fuzzy blob of pixels does impossible stuff and therefore is extraterrestrial" are destined to fail from the start.
 

Ann K

Senior Member.
A similar division is between the physical world and the spiritual word: thoughts are not things. The physical world is sometimes called the "natural world". Phenomena that go beyond the physical world are then supernatural
Thoughts are not objects, but are indeed physical actions. Thinking is, in that respect, analogous to walking, and neither can be accomplished without bodily actions. The fact that we cannot see electrical impulses is immaterial; they're still part of the natural world.
 

johne1618

Active Member
I have great confidence in the laws of physics. I couldn't rate any witness report as "90% certain" that involves violating a physical law.

The idea of my reverse Bayesian argument is to start by estimating the likelihood of a normal explanation for the evidence as a whole without any prior prejudices. Only later does one deduce the prior probability of the paranormal required to “balance” that likelihood of a normal explanation leaving a 50% posterior belief in the paranormal.

My problem with Carl Sagan’s “Extraordinary claims require extraordinary evidence” is that it squashes each individual paranormal claim without allowing a group of good cases to be combined to offer support for the paranormal.
 
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LilWabbit

Senior Member
Sorry I'm late to this party.

Let A = Hypothesis that aliens are visiting Earth

Let Not[A] = Hypothesis that aliens are not visiting Earth

Let { CE_i } = A set of i independent Close Encounter events

Using Bayes' theorem we find...

Confusion of necessity (or 'affirming the consequent') is a fallacy in formal logic which the OP perpetrates in a number of ways.

Based on the valid inference rule modus tollens (or 'denying the consequent'):

(1) The proposition 'there has been a report of a close encounter event' is not a logical (necessary) consequence of either the proposition 'aliens have visited earth' nor the proposition 'aliens have not visited earth'. If the proposition 'aliens have not visited earth' is true, the proposition 'there has been a report of a close encounter event' could still be true (while referring to an honest report).

(2) If the proposition 'aliens have visited earth' is true, the proposition 'there has never been an actual close encounter event' could be just as true as the propositions 'there has been a report of a close encounter event' or 'there has been an actual close encounter event'.

(3) Thirdly and obviously, the proposition 'there has been a report of a close encounter' does not logically imply 'there has been a close encounter', nor does the proposition 'there have been hundreds of thousands of reports of a close encounter' logically imply 'at least one of them concerns an actual close encounter'.

The foregoing unwitting violations of modus tollens inherent in the initial conditions at the start of the OP renders all the ensuing discussion on the Bayes' theorem -- both in the OP and on the thread -- irrelevant and an entirely unnecessary derail.
 

Domzh

Active Member
sorry I'm late to this party
at least you bring the good stuff:
(3) Thirdly and obviously, the proposition 'there has been a report of a close encounter' does not logically imply 'there has been a close encounter', nor does the proposition 'there have been hundreds of thousands of reports of a close encounter' logically imply 'at least one of them concerns an actual close encounter'.

I believe the (root?) cause why so many fall for this trap can be found in publication bias.

People usually dont share their "no ufo" encounter (I would have loved to say "no hot dog" but fear many wouldnt understand...).

"Hey reddit, day #3625 of me seeing another bird in the sky"
 

LilWabbit

Senior Member
at least you bring the good stuff:

I believe the (root?) cause why so many fall for this trap can be found in publication bias.

I'm sure that's one valid cause. The other major one being our natural tendency to believe convincing declarations, especially when they come in great numbers. An all-around sensible person who sincerely shares his observation and insists on it being the truth, reinforced by many 'similar' stories the world over, can be a powerful sell. It takes a rare detachment and independence of mind to not be affected at all. A project of intellectual empowerment that MB has indeed taken on.

People usually dont share their "no ufo" encounter (I would have loved to say "no hot dog" but fear many wouldnt understand...).

:)

"Hey reddit, day #3625 of me seeing another bird in the sky"

A windblown plastic bag #666 for me. :cool:
 

Mendel

Senior Member.
I believe the (root?) cause why so many fall for this trap can be found in publication bias.
Not really, the trap is logic reversal.

This is true:
• Close Encounters cause UFO reports (theoretically) with some chance.

The false logic reversal is:
• UFO reports prove Close Encounters, with some chance.

And that's just not true; it does NOT follow logically from the first statement at all.
And therefore it's completely irrelevant what number of reports (or, as you suggest, non-reports) we have, as it fails to give us valid information.

Only an actual verifiable UFO report could do that, and one (1) would suffice! but there isn't one. (Hence my use of "theoretically" above.)
 

Domzh

Active Member
fully agreed.

i first thought the amount of people falling for this trap could be increased by publication bias. but you are right, its not connected.

there could be 10000^x "non ufo" reports versus 10^x "ufo" reports and they would still form the same nonsensical suggestion like:

"Its insane to think that so many people misinterpret a balloon, but for the sake of the argument assume a super low probability of them being correct."

The issue remains that by doing this, they inherit that the accepted hypothesis is already set to "ufos are real" because they attribute a probability higher than 0 even if they fail to realize what they just did.

They basically say "Lets find out what the chances of a ufo report being correct is by assuming that ufos are real. And if only every 1:100000^x is real, then this means ufos are real".

which qualifies as a "circular argument" long before doing any calculations.
 
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