Circular reasoning

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Circular reasoning is a form of proof by assertion, often used by Atheists and evolutionists in which one uses a conclusion of an argument as a premise to that same argument, that is, ending where it began. This is also known as petitio principii or begging the question. It is considered invalid and therefore is not permitted by the rules of formal logic. Nevertheless, circular reasoning is the current trend in science or rather postmodern science, respectively, when new discoveries are interpreted within the prevailing paradigms so as to appear to bolster it, especially by using the popular media.[1]

An example of flawed circular reasoning is to rely entirely on carbon dating to determine whether the Shroud of Turin is miraculous, as a miraculous imprint could have altered ordinary decay of the material.

An analysis

The simplest argument is a single inference, as per the Law of Detachment:

  • If P, then Q.
  • P.
  • Therefore, Q.

The Law of the Syllogism uses Detachment to establish an intermediate conclusion between the original premise and the eventual conclusion. Thus:

  • If P, then Q.
  • If Q, then R.
  • Therefore, if P, then R.
  • P.
  • Therefore, Q and R.

Contraposition uses Detachment in reverse to show that a thing is not true:

  • If P, then Q.
  • Not Q.
  • Therefore, not P.

All these proofs start with a proposition already verified or denied.

This is the classic structure of circular reasoning, that is an abuse of the Law of the Syllogism:

  • If P, then Q.
  • If Q, then R.
  • If R, then P.
  • P.
  • Therefore, Q.
  • Therefore, R.
  • Therefore, P.

Each of these three conditional statements would be valid by itself. Together, they create a flawed argument, because P now depends on itself to be true. The line of reasoning ends where it began, and is thus a circle. The only difference between this and proof by assertion is that the latter attempts to use a single conditional statement--"if P, then P"—while circular reasoning uses at least two, and typically three or more, syllogisms.

Circular arguments can be very difficult to detect. Circular arguments found in the professional literature, or in propaganda, typically use five or six (or more) syllogisms.

Every logical system must begin with a set of generally accepted assumptions called postulates or axioms (from the Greek αξιος or axios worthy or deserving). Similarly, any set of definitions must start with a set of fundamental terms that need no definition. An axiom is usually a fundamental property of nature upon which all agree. Persons attempting to show that something is a fundamental property of nature when it is not, or a value of that property that is contrary to fact, typically use circular reasoning to make such an attempt.

Begging the question

Begging the question is a form of circular reasoning in which a claim is automatically assumed to be true without evidence other than the statement or claim itself. The phrase is commonly confused with "raising the question," an error that has gained traction through incorrect popular usage.[2]


  • Atheists use circular logic to "disprove" the existence of God. That is, they presuppose that God does not exist and then argue that all proofs for the existence of God must be flawed because He does not exist. Christians can use presuppositional apologetics to break the circle of the atheists' circular reasoning.
  • Muslims also use circular logic to defend the Qur'an. They argue that the Qur'an is true because it is the Word of Allah, that it is the Word of Allah because it says so, and that we can rely on it because it is true.
  • Mormons and certain Protestants use circular reasoning to prove that a Great Apostasy occurred early in Christianity, based on the assertion that their own doctrines represent New Testament Christianity and that Catholicism and Orthodoxy are clearly apostate, from the fact that Catholic and Orthodox doctrines are evident in the writings of the Apostolic and Ante-Nicene Fathers before A.D. 325 and so clearly refute the doctrinal claims of Mormons and Protestants against Catholicism. See Memory hole and Revisionism.
  • "If such actions were not illegal, then they would not be prohibited by the law."
  • Person 1:"He is very ugly."
Person 2: Why do you say that?"
Person 1: "Because he is so unattractive."

See also


  1. Alex Williams, John Hartnett (2005). Dismantling the Big Bang. Green Forest, AR, USA: Master Books, 269. ISBN 978-0-89051-437-5. 

External links