Wishful Thinking



I want P to be true.
Therefore, P is true.


…[I]t is a habit of mankind to entrust to careless hope what they long for, and to use sovereign reason to thrust aside what they do not desire.


Source: Thucydides, The Landmark Thucydides, edited by Robert B. Strassler, p. 282.


I was attending a spiritualist message reading service. The guest speaker had each of us write our name and a question on a piece of paper and then fold the paper. An usher collected the folded messages in a basket which she then placed beside the speaker's lectern. The speaker, who had been blindfolded, would reach into the basket, pull out a folded message, and hold it to his forehead. After a dramatic pause he would call out someone's name. The named person would then stand and the speaker would provide an answer to the question. Presumably this answer was supplied by the spirits. …

… On this occasion, however, the speaker was having obvious difficulties. He was getting along in years and his eyesight was not very good. … So he pulled his blindfold away from his eyes with one hand while he blatantly opened the message with the other. After he read its contents, he refolded it, pulled his blindfold back in place, and continued with his routine.

I looked at the members of the audience to see how they would react to this obvious display of cheating. … To my surprise, not one of them was looking at the speaker. Some were gazing at the ceiling, some were staring into their laps, and others had their eyes closed. The woman sitting next to me was one of those looking at the ceiling. I nudged her and pointed to the speaker at the moment he was opening a message. She looked at me instead. I whispered for her to look at the speaker. She turned and looked at the back of the room and then turned back to me. I kept urging her to look at the speaker. She leaned back and resumed staring at the ceiling.

This bizarre behavior by the audience both puzzled and amazed me. … These people did not want to see the speaker cheating! They wanted to believe that he was providing them communications from their departed loved ones. … They dealt with this conspicuous example of cheating by simply not looking. …

Source: Ray Hyman, "Foreword" to The Psychic Mafia, by M. Lamar Keene, Prometheus, 1997, pp. xiii-xv.


Psychologically, "wishful thinking" is believing something because of a desire—"wish"—that it be true. As a logical fallacy, Wishful Thinking is an argument whose premiss expresses a desire for the conclusion to be true.

Of course, this type of thinking seldom takes the explicit form of an argument from a premiss about one's belief to the conclusion that one's wish is true. Such bald wishful thinking would be patently fallacious even to the wishful thinker. Rather, wishful thinking usually takes the form of a bias towards the belief in P, which leads to the overestimating of the weight of evidence in favor of P, as well as the underestimating of the weight against. As in the case of the Example, it can lead to ignoring the evidence against a cherished belief, which is a case of one-sidedness.


Wishful thinking has been practiced under such names as "positive thinking", "optimism", "visualization", and "faith". Under these names, it has had its distinguished defenders. Defenses of wishful thinking have taken one of the following forms:

  1. Moral/Ethical Defenses: Religious faith has frequently been claimed to be either a virtue or a duty. To believe a dogma without evidence, or even despite counter-evidence, is sometimes regarded as more admirable than to believe on good evidence. Unfortunately, this doctrine itself must be taken on faith, as there is no evidence for it!
  2. Pragmatic/Prudential Defenses: A pragmatic or prudential defense of wishful thinking is based on the claim that one stands to gain from such belief, and that this is a sufficient reason to believe. William James' famous defense of "the will to believe"—that is, wishful thinking—is of this type. James argued that there can be pragmatic value in believing something by an act of will, when there is insufficient evidence to justify belief or disbelief. If there is pragmatic value in believing a truth, but no evidence for it, then the only way that one can gain that pragmatic value is by a "leap of faith".

    The thing to notice about the pragmatic/prudential defense is that it does not claim that the statement believed on faith will actually be true, or is even likely to be true. Rather the claim is that one can gain in some way by believing something that may be false for all that. While this may well be true, it is neither a logical nor epistemological defense of wishful thinking, unless—like James—one equates pragmatic value with truth.

    Suppose I offer a prize of a million dollars to anyone who believes that pigs have wings. There is no doubt that, if you can only force yourself to do so, you stand to gain from believing this. However, the fact that you win a million dollars in no way tends to show that pigs have wings.

The trouble with both of these defenses is that they do not show that wishful thinking is ever cogent, instead they support the following types of argument:

  1. P is an article of faith.
    Therefore, I ought, morally, to believe P.

  2. I stand to gain from believing P.
    Hence, I should, prudentially, believe P.

But from the conclusions of either of these arguments, it does not follow that P is true, or likely to be so. So, Wishful Thinking is still a fallacy, even if we accept that it is sometimes the virtuous or prudent thing to do.


T. Edward Damer, Attacking Faulty Reasoning: A Practical Guide to Fallacy-Free Arguments (Third Edition) (Wadsworth, 1995), pp. 96-98.


William James, The Will to Believe and Human Immortality (Dover, 1985).

Acknowledgment: Thanks to Steven Gardell for the Thucydides quote, which he mentioned in a letter to the editor of the Skeptical Inquirer, November-December 2006, p. 66.