Critical Thinking 18: Ad Hoc Argument

An ad hoc argument is one in which a person shifts their goals or ‘moves the goalposts’ in mid-argument in order to avoid having to admit that they’re wrong. It tends to accompany defensiveness and a dogmatic attachment to a position that can’t possibly be accepted as wrong without losing face.

It’s also sometimes known as the ‘No True Scotsman’, from an example in which a Scotsman who claims that no Scotsman eats his porridge with sugar, when challenged with a counter-example of one who does, rejoins that no true Scotsman eats his porridge with sugar. The claim about the Scotsman in this example has thus shifted to a claim about a much more flexible and manipulable ‘true’ Scotsman. The ‘truth’ of the Scotsman seems to amount to nothing more than the favour of being defined as such by the ad hoc arguer, but of course ‘true’ sounds terribly grand and may deceive the unwary, even though it turns out to be empty bluster when examined more closely.

More controversial contemporary versions of the ‘true Scotsman’, may include the ‘true Muslim’, the ‘true scientist’ or the ‘true Socialist’: the true Muslim may always be peaceful, the true scientist always provisional, and the true Socialist always committed to equality, thus allowing us to hang on to idealisations of these positions when challenged with counter-examples that show them to be rough labels for diverse traditions. It may still be the case that the overwhelming majority of Scots refuse to eat their porridge with sugar, and the overwhelming majority of Muslims are peaceful, but if we absolutely essentialise those categories it may be a way of repressing recognition of the minority who are not.

Another example of ad hoc argument is illustrated by the following cartoon, which is a version of a historical example from the life of Galileo. Here it is not the category of ‘Scotsman’ that is being defended, but an Aristotelian scientific theory that all celestial bodies from the moon upwards must be perfect spheres. In order to avoid questioning this theory, one of Galileo’s opponents came up with this highly implausible explanation of what he observed. Of course, it’s just possible that he might be right, but the defensive intention is pretty transparent (if you’ll forgive the pun).


Ad hoc argument departs from the Middle Way because it involves an absolutisation of the belief that is being defended. It is so absolutised that the alternatives being offered are just not seriously considered, and instead the person using the ad hoc argument just wants an excuse to dismiss the alternative. As with any absolutisation, it also has an opposite that is just as unhelpful, which in this case is the assumption that the theory being defended is unquestionably wrong. The problem with the transparent substance is not that we know it to be wrong, but that it is necessarily assumed to be right for defensive reasons, just as the problem with assuming all ‘true’ Muslims to be necessarily peaceful is not that there may not be a justifiable interpretation of Islam that would require peaceful behaviour, but that the assertion about ‘true’ Muslims is made to avoid acknowledgement of the violent ones who at least use the label ‘Muslim’.

Ad hoc argument is closely related to confirmation bias, the tendency to select from our experience and interpret it in terms of our existing beliefs. It can also be seen as a form of circular argument or ‘begging the question’. For example, in the Galileo example, Aristotle’s theory is supported by the belief that the moon is perfectly spherical despite appearances to the contrary, which in turn justifies the belief in Aristotle’s theory.

Ad hoc argument needs to be distinguished from some other reasons people may have for changing their position in the course of an argument. For example, it may be necessary to redefine one’s terms in the course of an argument in a way that is not defensive, but rather has the goal of reaching a helpful conclusion. For example, if you were having an argument about Christianity and started off with a very narrow definition of it (e.g. belief that Jesus is the son of God, meaning a supernatural entity), but then recognised that you could reach a more helpful agreement with another person by recognising that Christianity could be defined in different ways (e.g. as a symbolic or archetypal relationship with a Christ-figure within our experience), shifting your definition would not be ad hoc argument. In the end, it’s the unhelpful disruption to engagement and mutual understanding involved in a particular shift in position that makes it ad hoc, not the mere fact of shifting one’s position.


Are these examples of ad hoc argument?

  1. The ‘Leave’ Campaign in the UK EU referendum pointed out that there have been 72 occasions (since the 1990’s) when the UK disagreed with new EU laws but was overruled. They argued that this involved unacceptable infringement of UK sovereignty.  However, the ‘Remain’ campaign responded that these 72 occasions should be seen in the context of over 2000 occasions when the UK has agreed with new EU laws, so that seen as a proportion rather than as a raw number it was not very high.
  2. In a debate before a football game between England and Germany, an England fan predicted that England would win the game. In the event, England scored one undisputed goal, but Germany scored two goals, both from penalties awarded in controversial refereeing decisions. After the game, the fan argued that he had been correct, because England should have won the game if the referee had been fair.
  3. Two Christians are discussing the interpretation of the Bible in relation to the ordination of women, which one supports but the other opposes. In 1 Corinthians 14:33-35 it says: “As in all congregations of God’s people, women should keep silent at the meeting. They have no permission to talk, but should keep their place as the law directs. If there is something they want to know, they can ask their husbands at home. It is a shocking thing for a woman to talk at the meeting.” The first Christian argues that this passage clearly implies that women should not be ordained, as one could hardly be an ordained priest or minister and not speak at a church service. The second argues that Paul’s motive when he wrote this passage was to prevent conflict between early Christians and the surrounding Roman culture, and that there is no reason why it should be interpreted as a commandment for Christians today.

Link to index of other Critical Thinking blogs in this series

About Robert M Ellis

Robert M Ellis is the founder and chair of the Middle Way Society, and author of a number of books on Middle Way Philosophy, including the introductory 'Migglism' and the more in-depth 'Middle Way Philosophy' series. He has a Christian background, and about 20 years' past experience of practising Buddhism, but it was his Ph.D. studies in Philosophy that set him on the track of developing a systematic account of the Middle Way beyond any specific tradition. He has earned his living mainly by teaching, and more recently by online tutoring.

6 thoughts on “Critical Thinking 18: Ad Hoc Argument

  1. The only example above where one of the two parties changes their argument to avoid having to admit being “in the wrong” is number 2.

    I bring up what might be something analogous to the “no true Scotsman” fallacy when teaching thermodynamics at A level. Person A says “Gases behave according to the law pV = nRT”. Person B says, I’ve got a gas here and I’ve tested it and its behaviour is not described by that law”. Person A says “All *ideal* gases behave according to the law pV = nRT”. It’s not a logical fallacy, but it draws attention to what we mean when we use the term “ideal gas”. We certainly don’t mean that it is some model of perfection that all real gases somehow ‘fail’ to live up to. Many students are surprised when they realise that the so-called laws of physics work for the situations in which they work, rather than being some kind of Universal Truth.

  2. After some further consideration, maybe example 1 involves some moving of the goal by the Remains. Just because the proportion is small doesn’t mean that the Leave point is wrong. The Leaves could be arguing that *any* over ruling is an infringement of UK sovereignty. The fact that it is only a small proportion would not invalidate this argument.

  3. Thanks for the further example, Jim.

    I think no. 1 could only be ad hoc if the Remain side had previously sought to argue in terms of total numbers and then switched to proportions, but I can’t see any sign of them having done that. It’s just a counter-argument in which the possibility of thinking in proportions (giving one a more adequate understanding of the issue) is raised.

    I agree that no.2 is straightforwardly ad hoc.

    No. 3 is an interesting kind of case. I don’t think this example is ad hoc, because there’s no sign of the second Christian switching his criteria in mid-stream, only of him offering different criteria from the first. But there are plenty of examples similar to this in which religious believers appealing to a scripture switch to a more liberal way of interpreting it only when the going starts to look more challenging. My question in such cases is often why a religious scripture needs to be invoked at all if the justification of what it is believed to be significantly saying lies so much more in the experience of the people concerned than in the scripture.

  4. A massive example of ad hoc thinking is embodied in the petition on the UK government website that now seems likely to shortly hit 2 million signatures. This petition calls “upon HM Government to implement a rule that if the remain or leave vote is less than 60% based a turnout less than 75% there should be another referendum.” No such rule existed before the referendum, but the petitioners now want to move the goalposts! You can see the petition on .

  5. I can see the attraction, and considered signing it myself. Effectively, I think the supposed ‘rule’ being invoked has become irrelevant. The idea of an ad hoc rule of that kind is fairly obviously ridiculous, and the petition was original posted before the referendum when it wouldn’t have been ad hoc. But effectively it’s simply become a petition for a second referendum, which nobody is going to reformulate now because it has so many signatures. If enough people have plainly changed their mind, I hope the government will too. It will be very interesting to see how they respond.

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