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A clever person with bad motives is dangerous, as they can generate persuasive arguments to serve their interests rather than truth.

Julian Baggini (1968-)

Equivocation

When I was writing my blog about types of fallacies last week, I realized that I had given hardly any attention to fallacies of ambiguity, while I regularly explained fallacies of presumption and relevance. This is not surprising for in Arp et al. 2019, 43 fallacies of presumption and 34 fallacies of relevance are discussed but only 16 fallacies of ambiguity. If this is a measure, then the latter are by far in the minority, which doesn’t involve, however, that they are less frequent. The only fallacy of ambiguity I discussed is the conjunction fallacy, while I mentioned the sorites fallacy only in passing. So, a good reason to treat such a fallacy now.
I think – though it is just a guess – that one of the most common fallacies of this type is the fallacy of equivocation. It often appears in discussions and political speeches. This fallacy involves that a word or phrase is used with different meanings in an argumentation. You may think: Of course, that’s a matter of false reasoning. However, the distinctions between the different meanings are often subtle and you may not see them or you must be a logical expert, and maybe also the speaker didn’t notice the mistake. Here is a clear case: “The loss made Jones mad [= angry]; mad [= insane] people should be institutionalized; so Jones should be institutionalized.”) [1] “Mad” has two different meanings here, so the conclusion doesn’t follow. Here is another rather simple example of this type: Only man [human] is rational, and no woman is a man [male]. Therefore, no woman is rational. [2]
However, an equivocation can be rather subtle, as said. Bertha Alvarez Manninen starts her explanation of the fallacy in Arp et al 2019 with an equivocation by Pres. John F. Kennedy, who said: “And so my fellow Americans, ask not what your country can do for you, ask what you can do for your country.” The equivocation is here, so Manninen, that first “country” refers to the elected officials and then to something like your homeland, nation, or your fellow citizens.
The equivocation is even more subtle in a case analysed by the philosopher Mary Anne Warren and discussed by Manninen: I quote (pp. 262=3:

“Typically, a common pro-life argument runs as follows:

(1) All human beings have a right to life.
(2) A fetus is a human being.
(3) Therefore, the fetus has a right to life.

Warren … argues that an equivocation is made here with the term ‘human being’. In the first premise, [it] is a moral term, denoting the kinds of beings who are ‘a full-fledged member of the moral community.’… In the second premise, [it] is a biological term, denoting a member of the species Homo Sapiens. … A useful tool for determining whether an argument commits the fallacy of equivocation can be applied here: replace the premises of the argument explicitly with the term having the same meaning and then gauge whether the argument is successful.

(1) All human beings (in the moral sense) have a right to life.
(2) A fetus is a human being (in the moral sense).
(3) Therefore, the fetus has a right to life.

Seen this way, Warren argues that the pro-life argument commits the begging of the question fallacy in Premise 2 by assuming the very thing that needs to be argued [, namely] whether the fetus is a human being in the moral sense of the term... That is not to say that the fetus isn’t such a being but rather that this is the very thing that need to be argued rather than assumed.”

So far the quotation. Of course, alternatively one can add “(in the genetic sense)” in the premises instead of “(in the moral sense)”, etc. What this example makes clear is that discovering an equivocation often is hard, but it is necessary in order to get a meaningful debate. Its obscurity makes it an easy instrument of manipulation for politicians and orators by using ambiguous words or by using words in an ambiguous way.
However, you don’t need to be a politician, orator or a simple member of their public to commit the fallacy of equivocation. Also philosophers do, although they are supposedly experts in argumentation. Then we call it a category mistake. So, Heraclitus committed the fallacy of equivocation, or made a category mistake, when he said that you cannot step twice in the same river. By saying so, he confused the river and the water in the river. Another example is to confuse the mind and the brain. It is not our brain that thinks but our mind does. Also Descartes committed this fallacy, when he saw the mind sometimes as a thing and sometimes as a mental capacity.

Sources
- The numbers in brackets [ ] refer to the sources: Follow the links.
- Robert Arp; Steven Barbone; Michael Bruce (eds.), Bad arguments. 100 of the most important fallacies in Western philosophy. Oxford, etc.: Wiley Blackwell, 2019. Esp. Bertha Alvarez Manninen, “Equivocation”, pp. 261-5.

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The most dangerous liars are always those who believe they are telling the truth.

Thomas Metzinger (1958-)

Types of fallacies

In these blogs, now and then I write about fallacies. I think that this is important since the way we think has a big impact on the way we behave; on our private behaviour and our public behaviour. Therefore, it is better to avoid mistakes. As for public behaviour, one can think of political decisions and juridical verdicts, for instance. Especially, mistakes in juridical decisions can have dramatic consequences; for example, that an innocent suspect is sentenced to long prison terms, if not to the death penalty. Political decisions can lead to war or peace, so the reasoning that leads to such decisions must be sound. As for private behaviour, reasoning errors can have an impact on private life, such as wrong or too expensive purchases or voting for a president who doesn’t represent your interests, although you thought so. This time, I don’t want to discuss a special fallacy, but I want to give some background information.
Basically, there are two types of fallacies: Formal fallacies and informal fallacies. Both types of fallacies are based on incorrect deductive reasoning, but the difference is that in a formal fallacy, the conclusion doesn’t follow from the premises, because the structure or form of the reasoning is not correct, while in an informal fallacy the conclusion doesn’t follow from the premises because of the content of the argumentation. An important example of a formal fallacy we often come across in daily life is the “post hoc ergo propter hoc” fallacy (“post hoc ergo propter hoc” literally means “after this, so because of this”). An example: “If it has rained, the street is wet. This morning, when I woke up, the street was wet, so it has rained tonight.” This need not be true, for maybe a leaking tank lorry has passed. See this and this blog for more examples.
Although formal fallacies often happen in daily life, I think that informal fallacies are more frequent, especially in political discussions and other public discussions. Basically, there are three types of informal fallacies:
- Fallacy of presumption. It occurs, so Arp et.al (p. 22), “when an argument rests on some hidden assumption – it could be an unknown factor, a condition, set of circumstances, state of affairs, or idea – that, if not hidden, would make it clear that the assumption is not sufficient to be able to reason to (draw, infer) the conclusion.” The conjunction fallacy, discussed in one of my blogs (see link), is a case in point.
- Fallacy of relevance. It occurs, so Arp et.al (p. 25), when the premise or premises are irrelevant to the conclusion, even though they may appear so, because of an appeal to psychological or emotional relevance. Best known is the ad hominem fallacy (“playing the man instead of the ball”), discussed by me, for example, here and here. Also the “red herring” and “straw man” are fallacies of relevance.
- Fallacy of ambiguity. A fallacy of this type, so Arp et al. (p. 26), relies on some ambiguity (vagueness, obscurity, non-clarity) in wording or phrasing, the meanings of which shift/change to various degrees of subtlety during the course of the argument. The Sorites paradox is a case in point (“Take away again and again a grain of sand from a pile of sand; when is it no longer a pile?”) (see, for example, this blog). How often doesn’t it happen that the meaning of a word shifts during a discussion, or that it is so vague that you can use it for “any” conclusion by way of speaking?
This is how we often reason or how we try to convince others. But when we are doing so, we are on the wrong track.

Source
This blog is mainly based on the Introduction to Robert Arp; Steven Barbone; Michael Bruce (eds.), Bad arguments. 100 of the most important fallacies in Western philosophy. Oxford, etc.: Wiley Blackwell, 2019. 

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Groups and individuals with weak positions in society are faced with weak enforcement of their rights, while at the same time with strong enforcement of their duties. Conversely, groups with strong positions in society are well able to combine strict enforcement of their rights with weak enforcement of their duties.

Kees Schuyt (1943-)