Vicious Circle

Description:

The conclusion of the argument is appealed to as one of the truths or principles upon which the argument itself rests.

Examples:

"Jones is an honest man. I know this is true, since Jones told me so himself, and an honest man like Jones surely wouldn't lie about something like that."

"Everything Picasso draws is great art, even when he is just doodling on his napkin. By great art I mean whatever is done by a great artist, and Picasso is a great artist, because, of course, everything he does is great art."

Discussion:

Some of the most intractable problems in philosophy revolve around what either are, or at least appear to be, vicious circles. David Hume, for example, challanged the reliability of inductive reasoning as a whole by pointing out that scientists trust inductive reasoning solely because induction has tended to give reliable results in past observed cases, so it should continue to give good results in future cases as well. In short, they validate their use of induction by giving an inductive argument! Deduction is in no better condition. Lewis Carroll  (who was a professional logician and wrote children's books only as a hobby), wrote a clever dialogue between Achilles and a tortise to show that we apparently cannot justify reasoning on the deductive pattern known as Modus Ponens, without using Modus Ponens in our justification.

We are most inclined to use circular reasoning when we are trying to defend principles that are so fundamental to our reasoning that we cannot conceive of their being false. Hence we tend to rely on them even in a context in which they are supposed to be in doubt. I cannot, of course, solve fundamental epistemological problems in a short paragraph. However, it is important to remember that reasoning generally occurs in a context in which one thing is in doubt while other matters are not in doubt. Only some philosophers would subscribe to the view that a condition of being in doubt about everything makes sense. We are rightly accustomed to taking some things for granted, and surely among the beliefs we are entitled to take for granted (in most contextx) are the basic principles on which an argument is founded.

The fallacy of Vicious Circle mimics good reasoning, however, by relying on a principle of reasoning that we are not entitled to take for granted, but letting us assume that we are entitled to take it for granted. This may happen when we are trying to examine broad principles to see which ones we can properly take for granted in other contexts.

Source: In common useage the phrase "vicious circle" generally refers to a sequence of events that form a self-sustaining (but undesirable) feed-back loop, e.g. that giving foreign aide might discourage local production, keeping the local population poor, thus requiring that they receive foreign aide. I have so far not been able to document an early use of this phrase among logicians.

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