What is it called when someone does something irrational out of custom or habit?

For example, in the 1982 film, The Verdict, the case revolves around a medical document in which there is a discrepancy between an original document and a photocopy of that document. The defense argues that the photocopy is evidence that the original document had been altered and the photocopied version should be considered the authoritative record of what the document originally said.

The judge in the case rules against the defense because there is/was a legal principle that an original document always takes precedence over a copy of that document. However, this legal principle was established when copies of documents were made by hand and photocopy technology did not exist. So, essentially what is happening is that the courts are following an old custom that is illogical or irrational in light of modern technology. What is it called when this happens?

  • The etymological fallacy is a parallel concept. But your example doesn't work: the 'original document' must be at least as close to the original as even the most faithful copy. You're probably talking about how the so-called 'original document' looks now, and a photocopy of it hours after it had been written. Difficult with the Magna Carta, say. The stipulative definition I'm using: 'Original Document means the document itself in its original form' [LawInsider] Jun 5, 2021 at 15:25
  • 2
    Does this answer your question? A word that means outdated tradition ('outdated traditions or traditions that no longer make sense in the context of the modern day but that we still perform'). Jun 5, 2021 at 15:27
  • Aside: it is neither outmoded nor irrational. When a motor vehicle insurance company wants my "no claims certificate" they do want the original which was supplied by my previous insurer. They can tell the difference between the original and a copy, and refuse to accept the copy. The rationale is that I can only submit it to one insurance company, i.e. cannot obtain duplicate insurance. Jun 5, 2021 at 15:52
  • An outdated or antiquated evidentiary analysis method.
    – Lambie
    Jun 5, 2021 at 15:56
  • 1
    The example used is not exactly an example of the general question posed at the beginning. Legal rules are neither habits nor customs. It is not irrational for a judge to follow an established legal rule even if the rule itself is arguably irrational.
    – jsw29
    Jun 5, 2021 at 16:03

2 Answers 2


This is called Appeal to Tradition.

Appeal to Tradition is a type of logical fallacy in which something is accepted as true or better because it's the "way it's always been done." There is no evidence that a specific belief or course of action actually is better. It is just believed to be better because it is the traditional belief or course of action.

Examples of Appeal to Tradition:

  1. Church should begin at 11am because that's the time that we have always begun the church service.

  2. The cheerleaders should be allowed to wear their uniforms to school on Fridays because that's the way we have always done it. It is a tradition at this school.

  3. No one in this family has ever been divorced; therefore, you need to work out your marital problems. We don't get divorced!


Another related term for this is Ipse dixit.

The fallacy of defending a proposition by baldly asserting that it is "just how it is" distorts the argument by opting out of it entirely: the claimant declares an issue to be intrinsic, and not changeable.


  • 1
    Where is the first quote from, please? Please add links. Jun 5, 2021 at 15:34
  • @Edwin Ashworth: Done...
    – user405662
    Jun 5, 2021 at 15:38
  • 2
    Using some method of proving or disproving evidence is most definitely not an appeal to tradition. That could be, however, a type of arguement.
    – Lambie
    Jun 5, 2021 at 15:41
  • @Lambie: Methinks this definitely falls within the ambit of Appeal to Tradition. Still, I dunno. Maybe there's a better word/term, but my knowledge of legalese stops here. :)
    – user405662
    Jun 5, 2021 at 17:30

Edit: The legal term of irrationality or unreasonableness (also called Wednesbury unreasonableness) is one of the common law grounds of judicial review. That's when one court sanctions another when it sees that it has acted in the manner you describe. It means:

An irrational or unreasonable decision is one that was not reasonably open, as expounded by Lord Green MR in the Associated Provincial Picture Houses v. Wednesbury Corporation [1948] 1 KB 223.

Unreasonableness can include anything which can objectively be adjudged to be unreasonable. It is not confined to culpability or callous indifference. It can include, where carried to excess, sentimentality, romanticism, bigotry, wild prejudice, caprice, fatuousness or excessive lack of common sense” In Re W (An Infant) [1971] AC 682, per Lord Hailsham at 699H “a decision which does not add up” (R v Parliamentary Commissioner for Administration, ex parte Balchin [1998] 1 PLR 1)

a decision which no sensible authority acting with due appreciation of its responsibilities would have decided to adopt” (Secretary of State for Education and Science v Tameside Metropolitan Borough Council [1977] AC 1014, per Lord Diplock at 1064 E-F) (source: law oriented site)

Another law site says:

This is the most popular ground for a Judicial Review challenge and occurs where there is unfairness in the decision-making process that is so unreasonable as to be sustainable. It applies where the decision-making process was so unreasonable or irrational that it would not have been reached or executed by a reasonable decision-maker. The court will only accept this as a valid ground where there is clear evidence that no sensible person would have come to the same conclusion.

It is very difficult to prove irrationality or unreasonableness. The courts will only consider the decision-making process rather than the actual decision. It is not enough to show that the decision is unreasonable - it must be shown that the decision was completely outside of what is considered as reasonable.

More generally you could think of the term


the tendency not to change what is happening:

  • Many teachers were reluctant to use computers in their classrooms simply out of inertia. (Cambridge)

M-W defines it as

indisposition to motion, exertion, or change

Being reluctant to change is not always irrational, but whether it is or not becomes obvious from the context.

Not the answer you're looking for? Browse other questions tagged or ask your own question.