Ignoratio elenchi is a classic argument-based fallacy. It is a fallacy to be found in traditional logic: it’s important to note that as a fallacy it doesn’t necessarily entail an invalid argument. Ignoratio elenchi literally means “ignorance of refutation” and is sometimes known as the “fallacy of irrelevance” or the “fallacy of missing the point”.
Many take Oakeshott’s well-known invocation of ignoratio elenchi to be roughly coextensive with Ryle’s ‘category mistake.’ So the tourist wondering around the Oxford colleges, various institutes, the libraries and museums, administrative buildings and so on, who then inquires as to where the University is, is on Ryle’s terms committing a category mistake. This and several other similar examples are intended by Ryle to illustrate the absurdity of the dualist’s position – that mind and body can be spoken of in parallel ways. But though Oakeshott endorses Ryle’s anti-dualist critique, his deployment of the notion of a ‘category mistake’ is somewhat idiosyncratic.
Ignoratio elenchi is directly a logical rather than an epistemological term. It refers to any process of argument that fails to establish its relevant conclusion; or any counter-argument that fails to establish the contradictory of the proposition attacked. Ignorance would often lie behind these failures, of course, which brings in epistemology through the backdoor. A ‘category mistake’ need not involve any process of argument. A single proposition (“Green quadrilaterals dream furiously,” which contains a number of such mistakes) can exemplify a category mistake. A single proposition can’t exemplify ignoratio elenchi. Oakeshott’s use of the term ignoratio elenchi is tendentious in the sense that it’s only because he holds particular views that he regards certain arguments as failing to establish a relevant conclusion. For example: “The state is a human artifact . . . the proper goal of state action is to promote equality of distribution.” Because he understands the nature of politics in a particular way, Oakeshott regards any view about the promotion of a social ideal as misplaced in political argument.
So an argument which concludes that the state should promote equality of distribution involves a misunderstanding of the nature of politics (according to Oakeshott), and such a conclusion would always be an irrelevant answer to the question of what the state should do. But of course it’s a matter of opinion and dispute whether Oakeshott is right about the nature of politics, and hence whether the conclusion that the state should promote a social ideal really would involve ignoratio elenchi.
Putting this in the terms of a ‘category mistake’ – “Green quadrilaterals dream furiously” – is simply a logical howler on any ordinary understanding of the meanings of these words or concepts. But “The state should promote a social ideal of equal distribution” is only a logical howler on a particular understanding of the nature of politics – where ‘politics’ is an essentially contested concept if ever there was one. In this light, what is interesting about this is that Oakeshott’s position running on a particular view is, dare I say it, as self-contained as his adversary’s ‘demonstrative’ (rationalistic) political discourse, with its argument having the logical status of axioms within a system (or ideology).