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A moralistic fallacy (often, wishful thinking) is a logical fallacy that occurs when someone asserts that the way things should be is in fact how they are.
While cognitive dissonance (e.g. as in the fable of The Fox and the Grapes) describes the suffering experienced when holding an internally inconsistent worldview, utilizers of the Moralistic fallacy solve this discomfort by simply overwriting everything with how it should be, case closed - ta-daa, suddenly the world adds up.
 Alternative names
- wishful thinking
- appeal to hope
Wanting something to be true is irrelevant to its truth. However, if this belief were true, our wishes would always come true. Clearly, this is not the case.
Don't believe us? A toddler can't desire a cookie into existence; 6 million Jews couldn't desire themselves out of death camps.
- PETA and other animal rights activists have argued that milk is less healthy than alcohol, and even causes autism in the unborn.
- Some feminists may go beyond merely saying men and women ought to have equal opportunities to asserting that they do everything equally well, or that women do everything better.
- Infidelity is viewed as immoral by many, and so it must not be natural to desire other people than one's monogamous partner.
- Some fundamentalists' statements about Darwinism or homosexuality (which, in that latter case, also use the reverse).
The concern has been that evidence contradicting such moral values will lead to people justifying this behavior, since it is "natural". While understandable, this has led to instances in which research that contradicts them caused people uncomfortable with it to engage in denialism. In the realm of religion it can take the form "God is good, therefore He does not support X, which I view as bad." Alternately, it is possible for an atheist to make the opposite fallacious argument (as they are alleged to by some theists) that "I view God (or His commands) to be bad, therefore He does not exist."
 In public policy
Wishful thinking may characterize popular consensus on other important public policy issues. For example, American space policy is now in the grip of the belief that private firms will finance the exploration of outer space. For a while this seemed unlikely, but felt good because it offered an escape from spending the large sums necessary for human space exploration.
It should be stated, however, that this example may in fact become a reality. Elon Musk's SpaceX appears on the verge of bringing reliable, reusable rockets into the mainstream, promising to cut the cost of space missions by orders of magnitude. Other firms including Planetary Resources and Deep Space Industries were founded with the intent to (eventually) mine asteroids and ship the products around the solar system; even if reusable rockets become commonplace, building space hardware without having to rocket raw materials out of a gravity well is hoped to be substantially cheaper.
If this actually happens, we'll need a new example. Humans being the delirious life forms we are, though, there should be no shortage.
 Positive outcome bias
 Positive thinking versus wishful thinking
Wishful thinking is not the same thing as "positive thinking," or the idea that by thinking positively, one will experience better outcomes. Thinking positively can help a person achieve a particular goal, in much the same way that thinking negatively can be a demotivating factor; thinking positively can conceivably help someone to maintain their focus on getting some task done. Wishful thinking, on the other hand, is more about changing reality to match your perceptions, or thinking that reality would be swayed by what you think.
An apt analogy can be found in medicine. Thinking positively about a course of treatment can improve a patient's outlook on life, helping the patient to feel better and maybe even having a placebo effect. Meanwhile, wishful thinking would entail denying that one had an illness, or that God would cure it, and assuming it would go away just because of that.
 See also
- Appeal to nature: What is natural is good.
- Hume's law: The is/ought problem.
- Solferino fallacy: War is natural, and therefore good.
- Wishful thinking
- Appeal to consequences
- Appeal to emotion
- Escape to the future
- Word magic
- Law of Attraction
- Magical thinking
- Willful ignorance
- Logical Fallacies.info on the moralistic fallacy.
- Iron Chariots on the moralistic fallacy.
- Fallacy Files 
- Internet Encyclopedia of Philosophy 
- Wikipedia 
- Bruce Thompson 
- Global Tester 
- Skeptic's Dictionary 
- Gordon, Hanks, & Zhu