A lot of the motivation to post on these discussion forums is to try to change someone's mind. The formal study of how and why people change their minds is called belief revision, and it is only a few decades old. Argumentation skills, of course, were practiced for longer than written history.

 

Generally, to change someone's mind you either give them new information (that they believe) or show that they have a contradiction in their existing belief set. Given new information, they might simply add it to their belief set. To resolve a contradiction, they generally discard the "least useful" belief. For example, if someone has based their morality off of their religion, they are highly unlikely to reject their religious beliefs, and instead might modify them to accommodate the new fact, or reject the new information.

 

Some links:

Cognitive Dissonance

When what you do contradicts what you believe.

 

belief religion

 

RESOLVING CONTRADICTIONS[pdf]

 

Basically, just showing a contradiction in someone's beliefs, or sharing new information that contradicts their beliefs, doesn't guarantee that they will change the belief you might be trying to change.

Very interesting articles although the "belief religion" link was painfully dry. I've found through experience that the most effective way to change someone's mind is to make it seem like it was what they always believed anyway. This entails agreeing with them generally but challenging some minor point. Knowing that you agree with them for the most part, they will be more likely to concede a small point. From there you gradually shred there point of view issue by issue until they eventually drink the Kool-Aid.

Oops, the link that says "belief religion" should say "belief revision". I guess that one is a bit formal, using set theory and all that.