Ad Hoc Fallacy: Definition and Examples

Ad Hoc Fallacy: Definition and Examples - Fallacy in Logic

The Latin phrase “ad hoc” means literally translated “to this”. It refers to an idea or solution that is intended for a specific use, and not for any other uses.

Ad hoc fallacy, or ad hoc rescue, occurs when someone comes up with a rationale or explanation to dismiss the counter-evidence to their claim in a bid to protect it. 

Since the ad hoc rescue is not an actual argument, it technically cannot be a logical fallacy. However, it is often still classified as one because it’s used as a substitution for a proper argument.

What Is the Ad Hoc Fallacy?

Ad hoc fallacy is a fallacious rhetorical strategy in which a person presents a new explanation – that is unjustified or simply unreasonable – of why their original belief or hypothesis is correct after evidence that contradicts the previous explanation has emerged.

As such, it’s an attempt to protect one’s claim from any potential refutations and thus preserve their existing beliefs. Furthermore, the explanation is specifically constructed to be used in a particular case and is created hastily at the moment rather than being the result of deliberate, fact-based reasoning.


Here’s a couple examples of the ad hoc fallacy to better illustrate it:

Example 1

  • Student 1: “I really should have got an A for the exam.”
  • Student 2: “You got several questions wrong though.”
  • Student 1: “Well yeah, but that must be because the teacher is a real a-hole.”
  • Student 2: “She is actually very nice.”
  • Student 1: “She should’ve considered how hard I studied for the exam. I really deserved an A.”

Student 1 doesn’t want to let go of her belief; instead, she comes with a new explanation each time the previous one is seriously (and quite easily) challenged. In other words, Student 1 makes stuff up as he or she goes.

Example 2

Another example would be:

  • Brad: “The new sales manager, Jim, is the worst ever; the sales revenue has been in a downtrend since he was appointed at the beginning of 2020.” 
  • Angelina: “Perhaps it could be due to something else. I know Jim is an effective manager: He has significantly increased the sales of every company he’s previously worked for and has even received a few awards.” 
  • Brad: “He’s still an awful manager because he’s too strict. That lowers people’s morale.”
  • Angelina: “I don’t think he is too strict.”
  • Brad: “Well, he’s always breathing on my neck and watching my every move.”

Here, after Angelina points out that Brad’s reason for the manager’s incompetence is unwarranted, Brad finds new “evidence” to preserve the justifiability of his view.