Appeal to consequences

Dr. Sayer: We know that for a fact? Dr. Ingham: Yes. Dr. Sayer: Because? Dr. Ingham: Because the alternative is unthinkable. An appeal to consequences (also argumentum ad consequentiam) is a logical fallacy that the perceived outcomes of a proposition can determine its veracity. However, the utility of a belief is independent of its truth-value. Unlike most logical fallacies, this one doesn't even attempt to appeal to reality.

The fallacy is an emotional appeal and an informal fallacy.

Sometimes an appeal to consequences is called a pragmatic fallacy; this is incorrect. A pragmatic fallacy uses an example where something "worked" to argue for its general efficacy, while an appeal to consequences uses the effects of holding a belief to argue for the truth value of a proposition.

Alternate names

 * appeal to utility
 * appeal to convenience
 * argumentum ad convenientiam
 * appeal to consequences of belief
 * argument from adverse/beneficial consequences

Form
The argument takes this form:

Or, conversely:

Explanation
Truth matters in logical debates; our emotions or feelings about the truth do not. While human emotions, feelings, and values will always influence what we decide to do based on our knowledge of the situation, that knowledge cannot be unduly influenced by our emotions or values if it is to be true knowledge.

This is applied fallaciously in arguing whether something is true or not. Just because something is perceived as having adverse consequences if it is true, does not make it suddenly become untrue — such an idea is just a form of wishful thinking. Conversely, when something is perceived as having good consequences if it is true, this perception does not actually make it true. Any argument from consequences is an appeal to emotion.

Examples

 * Belief in the theory of evolution leads to eugenics; therefore the theory of evolution is false.
 * Belief in God leads to an increase in charitable giving; therefore God exists.
 * The existence of gravity would make falling from a height onto a hard surface unpleasant, therefore gravity cannot exist.
 * Reducing greenhouse gas emissions would require policies we don't like, therefore anthropogenic greenhouse gasses don't have any effect on the climate.
 * Fighting COVID-19 would require policies we don’t like, therefore COVID-19 is just the flu.
 * "An immortal life exists because without such a concept men would have nothing to live for. There would be no meaning or purpose in life and everyone would be immoral."
 * "I don't know how magnetic bracelets relieve pain, I just know that they do."
 * Christianity is true because it preaches love and caring for other people.
 * The Steady State theory lived on as long as it did because many of its proponents considered an eternal ever-continuing Universe to be more elegant and desirable (they're not wrong, reality unfortunately disagrees).
 * Trump supporters aren't racist because if you call them racist Trump will win a second term!
 * Bad things have been done in the name of religion, therefore religions are incorrect/false.

Sun Myung Moon:

Public policy
It is generally not fallacious if used in decision making with something that isn't objectively provable, i.e., is this desirable, not is it true. This is found in political decision making, where the consequences, positive or negative, must be taken into account. There is no "real" political position, such as a tax rate or drug policy.

In these cases, the power of arguing from adverse consequences is directly proportional to the strength of the premise: for example, a proposal to discontinue a particular medicine because there are mild adverse effects (e.g. hair loss) in a small proportion of the cases would generally be considered dubious, while discontinuing the medicine because of serious adverse effects (e.g. early death or deformed babies) would generally be considered reasonable.

Since most acts will have both good and bad consequences, many of them unforeseen and unintended, it requires great care to deploy the argument from adverse consequences properly. Even using adverse consequences in decision making can be fallacious in some cases. The most frequent logical fallacy in this regard is when relatively small adverse effects are used to argue against practices with highly significant positive outcomes, e.g. that racial integration is bad because we no longer maintain separate bathrooms and water fountains which results in job losses for plumbers.

Epistemological nihilism
In "If belief X then consequence Y", while consequence Y doesn't prove X true, consequence Y does prove Y "true" and 'If X then Y' "true". Epistemological nihilism is the position that knowledge itself is impossible, often argued for by appealing to skeptical hypotheses e.g., you don't know that the world was created 5 seconds ago and all your memories were created along with it as proof you have no knowledge of the past. Evil demons, brains in vats, philosophical zombies, and cleverly painted mules are all used to demonstrate the total absence of knowledge (supposedly). This idea would indicate that 'if X then Y' can never be proven true, which can be pseudo-countered with the argumentum ad baculum.


 * Bob argues for epistemological nihilism.
 * Alice throws something at Bob.
 * If Bob ducks, he must have known that not ducking would lead to pain.
 * If Bob does not duck, by his own logic, Alice had no way of knowing that throwing things could injure other people.


 * Repeat until Bob stops arguing for epistemological nihilism.

A humorous example that doesn’t actually prove anything at all, but has an emotional appeal to effectively deal with the most annoying of philosophy undergrads. Ducking in this example doesn’t actually entail knowledge, though the premise is defining it as such. It can simply be rejected. It is possible that someone believes it is true but also believes they could be wrong, and always acts on the assumption that they are correct. Logically inferring based on past experience doesn't violate the premise whatsoever — people don't need to be certain before they act, in the way Bob doesn't necessarily know the object will hit him or be large enough to cause pain, but might duck on instinct or reflex anyway. There is also the issue that this runs against the distinction between a simply true belief and that of knowledge.

Epistemic nihilism could be argued to be incoherent as it leads to a paradox. If a subject was to believe epistemic nihilism is true, and they are justified to believe such on the basis of skeptical hypotheses, then they would know that knowledge is impossible. Of course, knowing that knowledge is impossible implies that knowledge is possible. This demonstrates that this is actually a contradiction to say that one knows that knowledge is impossible. Therefore, knowledge must always be a possibility or it would be the case that someone knows that knowledge is impossible if such an impossibility can be demonstrated. On that basis no one can really state they have a justified belief in epistemic nihilism being true, the only coherent response to such skepticism is skepticism of said skepticism as to prevent the possibility of knowledge. This can never then rule out the possibility of knowledge making epistemic nihilism incoherent.

Modus tollens
This is of course not to be confused with argumentation by contrapositive, or modus tollens. It is not a matter that the consequence is subjectively/objectively bad/immoral/undesirable if it does not occur in real life. The argument would go like this:

An example would be the claims of psychokinesis. Assuming that people can in fact move things with their minds, even in simple acts such as Uri Geller's spoon-bending, there is no way to expect that everyone with such a power would be good or sane. People would be telekinetically snapping each others' necks left and right and we would definitely hear about that sort of thing on the news. Obviously, it can be deduced that, since society isn't a hotbed of psychokinetic violence like in the movies, these powers simply do not exist.