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“”We agree that presuppositional apologetics is the ultimate biblical approach to apologetics. The common accusation that the presuppositionalist uses circular reasoning is actually true. In fact, everyone uses some degree of circular reasoning when defending his ultimate standard (though not everyone realizes this fact). Yet if used properly, this use of circular reasoning is not arbitrary and, therefore, not fallacious.
|—Darius and Karin Viet, Answers in Genesis|
Begging the question or assuming the answer is a logical fallacy that occurs when the conclusion of an argument is used as a premise of that same argument; i.e., the premises would not work if the conclusion wasn't already assumed to be true.
It is often called circular reasoning, although sometimes it's considered distinct with the distinction that circular reasoning is:
- A implies B which implies A
Begging the question similarly takes the form:
- A implies B and A is only valid because B is assumed.
Circular reasoning is fallacious because reasoning and justification must start with the known and then determine the unknown - in the case of circular reasoning, it starts with the known and ends up with the equally known, thus it proves nothing.
- We shall prove that God exists.
- The order and magnificence of the world is evidence of God's Creation.
- Therefore, we know that God exists.
Here, it is assumed that God exists in order to satisfy the premise that "God's Creation" is evidence of his existence. There is no standalone argument here that connects existence to God's creation except the conclusion, which is that God exists. Note the slight structural differences in the argument to simple circular reasoning - the order of the world isn't implied by God's existence, but trying to use it as evidence of God's existence must assume he exists in the first place.
- We shall justify making abortion illegal.
- Abortion is unjust murder.
- Murder is illegal.
- Therefore abortion should be made illegal, since it is murder.
In this case, the conclusion (that abortion should be illegal because it is murder) is assumed to be true in order to compare it to murder in the first point. Essentially, the initial premise comparing abortion to murder remains unproved without any additional evidence.
More God stuff now. This one is so mind-blowingly circular that you'd think it was a straw man. However, most Biblical literalists use the Bible as their main proof of God, and using the Bible as any form of evidence for God must assume the following circular argument.
- The Bible tells us that it is the word of God.
- The word of God is infallible.
- Therefore the Bible is infallible.
- And as such, the Bible must be the word of God.
- The word of God is infallible.
- Therefore the Bible is infallible.
- We know that the Bible is true because there was a miracle witnessed by 500 people.
- We know that there was a miracle witnessed by 500 people because the Bible says so.
This argument has actually been made by several different people, one of them being Dinesh D'Souza. They tend to try to bolster these types of arguments by saying things like "How could the Gospel writers have gotten away with claiming this if it didn't happen? Wouldn't someone have called them on it?"
Admittedly, more advanced theologians - well, anyone smart enough to use the word "theologian" - aren't this stupid and some creationists and literalists do try to prove the Bible though other means. However, this usually tends towards hilarity rather than good scholarship. In a variant used by Jason Lisle - out of all creationists, a man who certainly should know better - states the same thing as:
- If the Bible were not true, logic would not be meaningful.
- Logic is meaningful.
- Therefore, the Bible is true.
Sure, premise no.1 comes directly from Lisle's special place, but it also assumes that not only is there a connection between logic and the Bible's truthiness, it must assume the Bible is infallibly true to make such a connection in the first place. Remarkably, those premises as stated aren't paraphrased at all. Of course, this isn't the only example of extreme circularity in Lisle's work (and he's only one of a number of creationists). In his proposed anisotropic synchrony convention (a shamelessly plagiarised attempt to circumvent the starlight problem) the actual content of the science becomes meaningless as his underlying reasoning is that the Earth is 6000 years old because his convention says it is, and the usual speed of light conventions cannot possibly be right because such conventions imply that the world is older than 6000 years. Most Flood geology works along similar lines. It first assumes the Earth is 6000 years old in order to reject all established geology, biology and physics, and then uses new conventions to show that the Earth must be 6000 years old, thus simultaneously validating both their beliefs and methodology.
 By definition
One of the ways that circularity appears is whenever someone tries to argue a point "by definition". Simply put, if you can define your terms any way you like, then you can conclude anything you like without deriving anything new - hence it's circular. It's very simple to do, and doesn't always require someone running to a dictionary to do it. Consider the cosmological argument for the existence of God, which postulates that there must be a some kind of uncaused cause that brought the universe into being. While this alone doesn't prove any particular god - Allah, Yahweh, Brahman, and so on - and theologians most likely know this, it can be used as proof if this first cause is God "by definition". However, this makes the logic as follows:
- We define God as the thing that created the universe.
- God created the universe.
- Therefore God exists and created the universe.
Simply substitute "God" for something with fewer religious connotations and it would easily highlight the bizarre circularity. Nothing stops us replacing "God" with the Invisible Pink Unicorn precisely because the argument is constructed almost spherically.
 Circular definitions versus circular arguments
Circularity is fallacious when used in an argument. However, if one wishes to define a word, one must use other words to do so. If one then defines those words in terms of other words, and those words in terms of other words, and so on, one must, since there are a finite number of words, eventually reach a point where there are words that are defined in terms of each other, and thus the definition is in some sense "circular". This phenomenon is inevitable and not necessarily fallacious; the issue is whether definitions are presented as "this is what I mean by these words" or "this is a statement about the world". The latter is fallacious, while the former is not. So, above, the definition is taken to not merely define the concept of "God", but to speak to God's existence, and is therefore fallacious. On the other hand, consider the following argument made against evolution: "Evolution says that more fit organisms will out-reproduce less fit organism. However, 'fitness' is defined as the property of being able to out-reproduce other organisms. This is circular." Since evolution is merely presenting the definition of "fitness", and is not asserting that is has proved anything about the actual world, this definition of "fitness" is not fallacious. Every area of study can be presented as making similar statements, for instance "Christianity says that God created the universe. However, 'God' is defined as the creator of the universe." Or "Physics says that acceleration is equal to force divided by mass. But force is defined as mass times acceleration."
 Proving equivalence
A circular argument does not prove that any of the statements involved are true, but it does prove that they are equivalent; that is, all of them have the same truth value (either all are true, or all are false). This in itself can be useful. Consider an n x n matrix A. All of the following statement can be proven:
- If the column vectors are independent, then A is invertible.
- If A is invertible, then A has a nonzero determinant.
- If A has a nonzero determinant, then the dimension of the null space is zero.
- If the dimension of the null space is zero, then the column space has dimension n.
- If the column space has dimension n, then the column vectors are independent.
Proving these statements does nothing to establish that A is invertible. It does, however, mean that "the column vectors are independent", "A is invertible", "A has a nonzero determinant", "the dimension of the null space is zero", and "If the column space has dimension n" are all basically the same statement, and only one needs be checked for any particular matrix, which is certainly a useful result.
 Psychological causes
Often, people beg the question without being consciously aware that they are doing so. They have so thoroughly internalized a belief that they are not able to rationally evaluate it. When a person has been taking something for granted for a long time, it's difficult to not think that it's "obviously true", and in no need of justification. Trying to remove such a premise from one's thoughts and trying to reason without it can be difficult; take, for instance, many people's attempts to reason in a number system in which A*B is not the same as B*A.
 The denial trap
Often, denying a circular argument can leave one open to accusations that oneself is actually the one engaging in a circular argument. Such an accusation can be the result of one's opponent being devious, or simply being so lost in their own nonsense that they are unable to reason rationally. Take Example 3 given above. One can counter this by saying "The Bible is not the word of God. Therefore, when it says that it is infallible, there's no reason to believe it. Since it's not infallible, there's no reason to believe that it's correct when it says it is the word of God." This counterargument can then be made to look like a circular argument itself.
 Confusion with term
- Warning: Pedantry Alert
Many people use the expression "begs the question" to mean "raises the question" - in the sense that they believe an important point is being overlooked in the argument given. For example; "If God created the universe, this begs the question of who created God." In this case, "raises the question" is the correct term. There are countless of examples of this misuse, meaning it is not incorrect because people know what it means. Therefore pointing it out is best handled by professional and qualified pedants only. The original meaning of begging the question comes from a bad translation of petitio principii, literally a request (or beg) for the premise, which explains this problem.
 See also
- Not Circular Reasoning: An article exemplifying circular reasoning from Creation Ministries International.
| Articles about logical fallacies|
|Affirming the consequent||Denying the antecedent|
Begging the question
|Fallacious argument styles|