Argument from precedent is a common fallacy

Fallacy

In logic and rhetoric, a fallacy is usually an incorrect argumentation in reasoning resulting in a misconception or presumption. By accident or design, fallacies may exploit emotional triggers in the listener or interlocutor , or take advantage of social relationships between people...

 in discussion, for example on committees or in meetings. It consists in saying that to act correctly in circumstances X would be inadvisable, in case others consider that this would set a precedent for acting in circumstances Y, where (it is argued) X and Y are superficially similar but (on close examination) are radically different. The Microcosmographia Academica

Microcosmographia Academica

Microcosmographia Academica, literally meaning "A Study of a Tiny Academic World" in Greek, is a short pamphlet on university politics written by F. M. Cornford and published in 1908. It has acquired a small cult following as a pessimistic view of academic politics presented in a readable and...

, published in 1908, cited this as one of the reasons why "nothing should ever be done for the first time".

The fallacy is similar to the slippery slope

Slippery slope

In debate or rhetoric, a slippery slope is a classic form of argument, arguably an informal fallacy...

 argument

Argument

In philosophy and logic, an argument is an attempt to persuade someone of something, or give evidence or reasons for accepting a particular conclusion.Argument may also refer to:-Mathematics and computer science:...

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