Ad Hoc Explanations, Causes, and Rationalization
Faulty Causation Fallacy
Strictly speaking, an ad hoc fallacy shouldn't really be considered a fallacy because it occurs when a faulty explanation is given for some event rather than as faulty reasoning in an argument. However, such explanations are usually designed to look like arguments, and as such, they need to be addressed - especially here, since they purport to identify causes of events.
The Latin phrase ad hoc means "for this [special purpose]." Almost any explanation could be considered "ad hoc" if we define the concept broadly because every hypothesis is designed to account for some observed event. However, the term is normally used more narrowly to refer to some explanation which is exists for no other reason but to save a favored hypothesis.
Typically, you will see statements referred to as "ad hoc rationalizations" or "ad hoc explanations" when someone's attempt to explain an event is effectively disputed or undermined and so the speaker reaches for some way to salvage what he can. The result is an "explanation" which is not very coherent, does not really "explain" anything at all, and which has no testable consequences - even though to someone already inclined to believe it, it certainly looks valid.
Examples and Discussion:
Here is a commonly cited example:
I was healed from cancer by God!
Really? Does that mean that God will heal all others with cancer?
Well... God works in mysterious ways.
A key characteristic of ad hoc rationalizations is that the "explanation" offered is only expected to apply to the one instance in question. For whatever reason, it is not applied any other time or place and is not offered as a general principle. Note in the above that God's "miraculous powers of healing" are not applied to all cancer sufferers, but only this one at this time and for reasons which are completely unknown.
Another key characteristic of an ad hoc rationalization is that it contradicts some other basic assumption - and often an assumption which is was either explicit or implicit in the original explanation itself. That is why, usually, an ad hoc statement is only applied in one instance and then quickly forgotten. Because of this, ad hoc explanations are often cited as an example of the fallacy of Special Pleading. In the above, the idea that not everyone will be healed by God contradicts the common belief that God loves everyone equally.
A third characteristic is the fact that the "explanation" has no testable consequences. What could possibly be done to test to see if God is working in "mysterious ways" or not? How could we tell when it is happening and when it is not? How could we differentiate between a system where God has acted in a "mysterious way" and one where the results are due to chance or some other cause?
The fact of the matter is, we can't - the "explanation" offered above provides us with nothing to test, something which is a direct consequence of having failed to provide a better understanding of the circumstances at hand. That, of course, is what an explanation is supposed to do, and why an ad hoc explanation is a defective explanation.
Thus, most ad hoc rationalizations do not really "explain" anything at all. The claim that "God works in mysterious ways" does not tell us how or why this person was healed, much less how or why others will not be healed. A genuine explanation makes events more understandable, but if anything the above rationalization makes the situation less understandable and less coherent.-->