The argument depends on assuming the truth of part of the argument. An example of CircularReasoning.

"I like chocolate because it tastes good, and it must taste good or else I wouldn't like it."

Also called BeggingTheQuestion.

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Consider:
* Some conditions are dependent on precedent mutual commitments and cannot be true unless commitments are fulfilled
** "A is married to B because B is married to A"
** ''This is not the same as AntecedentAssumedFallacy. Properly: "(1) B is married to A. (2) Marriage is commutative (from definition). (3) Therefore, A is married to B." No need to assume any antecedents, but one does need to reference the properties of 'marriage'.''
** In the wedding ceremony, the two parties make commitments which satisfy the marriage contract. One commitment precedes the other. The commitment is solemnized by an official either civil or religious. They become married because of the commitments, first of all of A to B, and then of B to A. The above statement is true, not false, because after A commits to marriage, B's commitment is sealed by the official. 
** [Um, under the AmericanCulturalAssumption you aren't married just because you've committed to the other.  You are married once you, your partner, the official, and the required number of witnesses, have signed the marriage contract.  In other words, A and B are married simultaneously.  (I know some states have common law marriages, but again, the marriage of A and B is still simultaneous.]
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See FallaciousArgument