This is an attempt to classify disagreement reasons, along with tips on working past impasses.

* Disagree with Authority (ArgumentFromAuthority)

* Too many variables - There are lots of metrics or evidence specimens, but the weights given to each is in dispute. (TooManyVariablesForScience)

* Definition - LaynesLaw

* Miscommunication (dreadfully frequent; sometimes results in ViolentAgreement)

* Differing set of accepted axioms

* Differing priorities, especially if these are not recognised

* Personality clash (biggest and most frequent cause of all)

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When you find yourself arguing with someone, even though they are basically right, it is time to quit, because you really don't have a legit reason for the argument.  The real reason being, "you just don't like the guy".