Wishful thinking

Wishful thinking is the formation of beliefs and making decisions according to what might be pleasing to imagine instead of by appealing to evidence or rationality.

Studies have consistently shown that, holding all else equal, subjects will predict positive outcomes to be more likely than negative outcomes. See positive outcome bias.

Prominent examples of wishful thinking include:
 * Economist Irving Fisher said that "stock prices have reached what looks like a permanently high plateau" a few weeks before Stock Market Crash of 1929, which was followed by the Great Depression.
 * Operation Barbarossa, Hitler's plan for the invasion of Russia.
 * President John F. Kennedy believed that, if overpowered by Cuban forces, the CIA-backed rebels could "escape destruction by melting into the countryside" in the Bay of Pigs fiasco.
 * President George W. Bush Jr hoped that at the time uttering "Mission Accomplished" his problems in Iraq were over

As a logical fallacy
In addition to being a cognitive bias and a poor way of making decisions, wishful thinking can also be a specific logical fallacy in an argument when it is assumed that because we wish something to be true or false that it is actually true or false. This fallacy has the form "I wish that P is true/false, therefore P is true/false."

For example:


 * The teacher gave us a difficult exam! We shouldn't have to be subjected to such stress under the course of our education.

It may be that it was uncomfortable, but that does not mean that uncomfortable things should always be avoided. Wishful thinking underlies appeals to emotion, and is a red herring.

Atheists argue much of theology, particularly arguments for the existence of God, is based on wishful thinking because it takes the desired outcome "God exists" and tries to prove it on the basis of a premise through reasoning which can be analysed as fallacious, but which may nevertheless be wished true in the mind of the believer. The same could perhaps be applied in reverse: the desired outcome of "god does not exist" preceeds arguments of proof.