Friday, March 2, 2018

Wishful thinking

Start with this observation:

  1. Commonly used forms of fallacious reasoning are typically distortions of good forms of reasoning.

For instance, affirming the consequent is a distortion of the probabilistic fact that if we are sure that if p then q, then learning q is some evidence for p (unless q already had probability 1 or p had probability 0 or 1). The ad hominem fallacy of appeal to irrelevant features in an arguer is a distortion of a reasonable questioning of a person’s reliability on the basis of relevant features. Begging the question is, I suspect, a distortion of an appeal to the obviousness of the conclusion: “Murder is wrong. Look: it’s clear that it is!”


  1. Wishful thinking is a commonly used form of fallacious reasoning.

  2. So, wishful thinking is probably a distortion of a good form of reasoning.

I suppose one could think that wishful thinking is one of the exceptions to rule (1). But to be honest, I am far from sure there are any exceptions to rule (1), despite my cautious use of “typically”. And we should avoid positing exceptions to generally correct rules unless we have to.

So, if wishful thinking is a distortion of a good form of reasoning, what is that good form of reasoning?

My best answer is that wishful thinking is a distortion of correct probabilistic reasoning on the basis of the true claim that:

  1. Typically, things go right.

The distortion consists in the fact that in the fallacy of wishful thinking one is reasoning poorly, likely because one is doing one or more of the following:

  1. confusing things going as one wishes them to go with things going right,

  2. ignoring defeaters to the particular case, or

  3. overestimating the typicality mentioned in (4).

Suppose I am right about (4) being true. Then the truth of (4) calls out for an explanation. I know of four potential explanations of (4):

  1. Theism: God creates a good world.

  2. Optimalism: everything is for the best.

  3. Aristotelianism: rightness is a matter of lining up with the telos, and causal powers normally succeed at getting at what they are aiming at.

  4. Statisticalism: norms are defined by what is typically the case.

I think (iv) is untenable, so that leaves (i)-(iii).

Now, optimalism gives strong evidence for theism. First, theism would provide an excellent explanation for optimalism (Leibniz). Second, if optimalism is true, then there is a God, because that’s for the best (Rescher).

Aristotelianism also provides evidence for theism, because it is difficult to explain naturalistically where teleology comes from.

So, thinking through the fallacy of wishful thinking provides some evidence for theism.


Martin Cooke said...

Naturalistically, animals tend to assume that things will go right because that makes each of them try their thing; the ones that succeed go on to reproduce. What would be the evolutionary point of an animal that could have done a successful thing, it had all the physical attributes, but that did not bother, because there was little chance of success? The answer would be to have a lot of offspring, each of which thought that things would go right.

Maybe I get the details wrong; but, given any such explanation, there is no evidence for theism.

I do wonder if the necessary improbability of deceptive demons shows that there is a God (following Descartes) though ...

Martin Cooke said...

That is, evolutionary pressures could have made 4 an indispensable part of good reasoning; good in a naturalistic, not a classically logical sense. (It would be similar to how we have, on pain of irrationality, to give a very low probability to skeptical scenarios, almost all of the time, even though we can have no idea how likely such scenarios really are.)

Another reason why 4 might be true is that we must always and inevitably be looking back on a successful getting to where we are. Had things gone very badly, we would not even be here; or we would at the very least be less rational than we are, etc. That is an anthropic reason, I guess.

Other than that, I do like your analysis of wishful thinking (although I personally have found that wishful thinking motivates me to attempt stuff that is then rewarding for incidental, unforeseeable reasons, while what I directly attempt does not go right at all!

Martin Cooke said...

That anthropic reason was for why evidence might show 4 to be true, of course, so I guess that it would not explain why 4 was true, after all.

Martin Cooke said...

And the evolutionary reason would not explain why 4 was true, of course, only why it was a good form of reasoning (were we not restricting those forms to truths).

Martin Cooke said...

Still, those two do thereby undermine the claim to evidence for theism.

Callum said...

Hi dr. Pruss,

Little off topic but I was wondering if you go into the PSR and modal collapse in any more depth in your new book in comparison with your previous work?

Alexander R Pruss said...

Callum: No, sorry. Alex

Alexander R Pruss said...


I like the move of distinguishing *epistemically* good forms of reasoning from forms of reasoning that are good in some other respect, say psychologically. But I am inclined to think 1 is true even if we restrict to epistemically good forms of reasoning.

Muslim Salik said...

Hi Alex,
Wishful thinking could be construed as fallacious reasoning, or as a cognitive bias. Would you say that all cognitive biases have rationally respectable origins? For example, confirmation bias could be the subconscious result of a crude understanding of epistemic conservatism.

Alexander R Pruss said...

I suspect that most if not all common cognitive biases are like that.

Alexander R Pruss said...

I suspect that most if not all common cognitive biases are like that.