Evaluating Arguments, Part 2: Circularity


Circular motion was long thought to be the perfect form of motion, and as a result, it was postulated as the way heavenly bodies moved around the Earth. While circular motion may (or may not) be the “perfect” form of motion, circularity is certainly nowhere near perfect in argumentation. It is, in fact, a pernicious fallacy that seeps into much of our reasoning and argumentation, many times unconsciously. Today we will be looking at one way to critically assess an argument, namely establishing that it is circular.

There are (roughly) two types of circularity:

Circular Argumentation

In circular argumentation, one or more of the premises (or the justifications fro he premises) presupposes the truth of the conclusion. It is essentially assuming the very thing in question. The conclusion is said to be “included in” (either implicitly or explicitly) a premise, or a premise is said to be “reliant upon” the conclusion.


P1: If determinism is true, then our giving each other praise and blame is meaningless.

P2: Our giving each other praise and blame is not meaningless.

C: Therefore, determinism is false.

This is arguably an example of question-begging. Premise 2 can only be justified by an appeal to free will, which is thereby an appeal to the falsity of determinism. Thus, premise 2’s truth can only be established by the truth of the conclusion, meaning the premise presupposes that the conclusion is true in order to argue for that very conclusion. This argument, therefore, is circular.

Circular Justification

This can also be called the “Cartesian Circle.” The following considerations regarding Descartes’ error are adapted from the previously linked article.

The Cartesian circle is a mistake in reasoning attributed to René Descartes. Descartes argued in the third of his Meditations that whatever one clearly and distinctly perceives is true: “I now seem to be able to lay it down as a general rule that whatever I perceive very clearly and distinctly is true.” (AT VII 35)

He goes on to argue for the existence of a benevolent God, in order to defeat his skeptical argument in the first Meditation that God might be a deceiver. He then says that without his knowledge of God’s existence, none of his knowledge could be certain.

The Cartesian circle is a criticism of the above reasoning that takes this form:

1. Descartes’ proof of the reliability of clear and distinct perceptions takes as a premise God’s existence as a non-deceiver.

2. Descartes’ proofs of God’s existence presuppose the reliability of clear and distinct perceptions.

Thus, Descartes’ argument is circular.

If A justifies B, then you cannot also have your justification of B be A.

Some more examples of circularity are found below.

Example: We know our senses are reliable because we all independently converge on the same beliefs about objects in the mind-independent world.

The problem is, we could only justifiably claim that we all independently converge on the same beliefs about extramental objects if we presuppose from the get-go that our senses are reliable. After all, if our senses are unreliable, then we clearly cannot reliably come to know by means of our senses that our fellow human beings agree with our claims about extramental objects. This proposed justification for the reliability of sensory perception therefore presupposes the very reliability of the thing needing to be demonstrated as reliable.


A philosophical/neurological zombie is a being that is physiologically indistinguishable from a human, but that has no mental states.

Philosopher of Mind David Chalmers argues that although such zombies are physically impossible, they are nonetheless metaphysically possible. A being which shares all your neurological properties but none of your mental properties is not contradictory.

But if philosophical zombies are metaphysically possible, then identity theory, a theory of mind which states that mental states are identical to physical brain states, is false.

If it is possible for there to be a being that has every single molecule and atom in its brain entirely the same as you — if it is indeed possible for you to have an exact zombie replica/counterpart — your mental properties cannot be your physical properties. In other words, mental states cannot be identical to brain states if it is possible to have one without the other. If A is B, then it cannot be possible to have A without also having B (and vice versa). Thus, claims the proponent of the zombies argument, identity theory is false.

However, this argument is circular. To claim that it is possible for there to exist a philosophical zombie (i.e. a being whose brain is molecule-for-molecule identical to a human’s but which lacks phenomenal consciousness) is just to claim that neurophysiological states are not identical to mental states. In other words, it is just to claim that the identity theory is false. But that’s the very conclusion that the zombie argument seeks to establish. You cannot argue from the possibility of zombies to the falsity of identity theory because the possibility of zombies assumes the falsity of identity theory. This is because if identity theory is, in fact, true, then it is simply metaphysically impossible for there to be zombies. One can only believe that a zombie is possible, then, if one is already committed to the claim that the mind is not identical to the brain. As such, this argument against the identity theory is circular.

For some, circularity is seen as a rather difficult concept, and that’s okay. I will below provide further explanations from philosophical dictionaries.

Circular reasoning

“This is reasoning that, when traced backward from its conclusion, returns to that starting point, as one returns to a starting point when tracing a circle. The discussion of this topic by Richard Whatley (1787–1863) in his Logic (1826) sets a high standard of clarity and penetration. Logic textbooks often quote the following example from Whatley:

To allow every man an unbounded freedom of speech must always be, on the whole, advantageous to the State; for it is highly conducive to the interests of the Community, that each individual should enjoy a liberty perfectly unlimited, of expressing his sentiments.

This passage illustrates how circular reasoning is less obvious in a language, such as English, that, in Whatley’s words, is “abounding in synonymous expressions, which have no resemblance in sound, and no connection in etymology.” The premise and conclusion do not consist of just the same words in the same order, nor can logical or grammatical principles transform one into the other. Rather, they have the same propositional content: they say the same thing in different words. That is why appealing to one of them to provide reason for believing the other amounts to giving something as a reason for itself.

Circular reasoning is often said to beg the question. ‘Begging the question’ and petitio principii are translations of a phrase in Aristotle connected with a game of formal disputation played in antiquity but not in recent times. The meanings of ‘question’ and ‘begging’ do not in any clear way determine the meaning of ‘question begging’. There is no simple argument form that all and only circular arguments have. It is not logic, in Whatley’s example above, that determines the identity of content between the premise and the conclusion. Some theorists propose rather more complicated formal or syntactic accounts of circularity. Others believe that any account of circular reasoning must refer to the beliefs of those who reason. Whether or not the following argument about articles in this dictionary is circular depends on why the first premise should be accepted:

(1) The article on inference contains no split infinitives.

(2) The other articles contain no split infinitives.

Therefore, (3) No article contains split infinitives.

Consider two cases. Case I: Although (2) supports (1) inductively, both (1) and (2) have solid outside support independent of any prior acceptance of (3). This reasoning is not circular.

Case II: Someone who advances the argument accepts (1) or (2) or both, only because he believes (3). Such reasoning is circular, even though neither premise expresses just the same proposition as the conclusion. The question remains controversial whether, in explaining circularity, we should refer to the beliefs of individual reasoners or only to the surrounding circumstances. One purpose of reasoning is to increase the degree of reasonable confidence that one has in the truth of a conclusion. Presuming the truth of a conclusion in support of a premise thwarts this purpose, because the initial degree of reasonable confidence in the premise cannot then exceed the initial degree of reasonable confidence in the conclusion” (Cambridge Dictionary of Philosophy).

From the Internet Encyclopedia of Philosophy:

“A form of circular reasoning in which a conclusion is derived from premises that presuppose the conclusion. Normally, the point of good reasoning is to start out at one place and end up somewhere new, namely having reached the goal of increasing the degree of reasonable belief in the conclusion. The point is to make progress, but in cases of begging the question there is no progress.


“Women have rights,” said the Bullfighters Association president. “But women shouldn’t fight bulls because a bullfighter is and should be a man.”

The president is saying basically that women shouldn’t fight bulls because women shouldn’t fight bulls. This reasoning isn’t making any progress.

Insofar as the conclusion of a deductively valid argument is “contained” in the premises from which it is deduced, this containing might seem to be a case of presupposing, and thus any deductively valid argument might seem to be begging the question. It is still an open question among logicians as to why some deductively valid arguments are considered to be begging the question and others are not. Some logicians suggest that, in informal reasoning with a deductively valid argument, if the conclusion is psychologically new insofar as the premises are concerned, then the argument isn’t an example of the fallacy. Other logicians suggest that we need to look instead to surrounding circumstances, not to the psychology of the reasoner, in order to assess the quality of the argument. For example, we need to look to the reasons that the reasoner used to accept the premises. Was the premise justified on the basis of accepting the conclusion? A third group of logicians say that, in deciding whether the fallacy is present, more evidence is needed. We must determine whether any premise that is key to deducing the conclusion is adopted rather blindly or instead is a reasonable assumption made by someone accepting their burden of proof. The premise would here be termed reasonable if the arguer could defend it independently of accepting the conclusion that is at issue” (IEP).

One lesser-known and lesser-used form is circularity is epistemic circularity.

“An epistemically circular argument defends the reliability of a source of belief by relying on premises that are themselves based on the source. It is a widely shared intuition that there is something wrong with epistemically circular arguments” (Epistemic Circularity).

Author: Joe

Email: NaturalisticallyInclined@gmail.com

Sources: https://en.wikipedia.org/wiki/Cartesian_circle



Epistemic Circularity


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