For most applications critical reading and the application of general knowledge is enough to determine the relative truth of some thing. You make these distinctions everyday, hundreds of times, without even thinking about it. It's how we can have sarcasm.I agree with FG too, but how do you know what references to trust? Most of our silly thoughts are based on what we 'feel' is right.
So maybe we all should not argue to begin with because more than likely we are all wrong.
Science has their method, that being truth is an ongoing process made up of empirical and independently reproducible facts, the theories that would logically support those facts, and falsifiability of the theories (demarcation, that it is logically possible to be shown false, I cant explain it without using too many words).
Humanities usually uses logical consensus of the best available evidence and the largest number of independent sources. It's not usually important that an art is shown to be 'true' though. History has an entire method of research based on primary sources. >.>