I expect we've all had discussions IRL and online that seemed to consist of people talking past each other and getting more and more irate as their words fail to connect.
Underlying this is an interesting and uncomfortable fact of philosophy and humanity:
We don't all agree on what matters in a particular subject. We do not all agree on what is relevant.
This may sound dull and obvious, but this lack of agreement can carry a great deal of passion with it. What is vital in one person's life can be automatically dismissed by another person.
To some people this action is inconceivable. How can the most important thing in the universe mean nothing to someone else?
We see this behavior in nearly every aspect of life.
Fans of different activities (sports, books, movies, games) often have a hard time believing that others don't care at all about their fandom.
People who care about other people (their own families, for example) often cannot accept that others do not share that interest.
And here's the reason why I'm posting this in this board:
Member of religions and adherents of particular philosophies often find it impossible to believe that non-members find the concerns of that religion or philosophy irrelevant to the lives and thoughts of others.
I'd like to venture the opinion that this disconnect is a far more common source of broken communication than the more glorified situation where people agree on relevance and disagree on right and wrong.
I don't want to list too many hot button issues that I think are driven by this fracture in relevance, otherwise I'd likely find myself in the ironic position of having to lock the thread I started.
Rather, I'd like to suggest analysis of the kinds of discussion subjects that do go up in flames in order to find incompatibilities of relevance.
It might seem unlikely that this conflict would cause thread-go-boom, but let's consider the kinds of visceral reactions that arise within discussion.
I submit that there is nothing so angering as having something we cherish treated as irrelevant.
It is also, in my experience, more difficult to convince people of relevance than it is to get them to change their views within an agreed-upon context. This leads to the escalating frustration that arises from trying, futilely, to direct someone else to consider the subject from a different perspective.
There is also a social complication in matters of relevance that can lead to a sense of impotence and helplessness or boiling-over rage.
One of the exercises of social power is the ability to declare a subject relevant or irrelevant.
A person who gets to choose what questions to ask, what items are on the agenda, what subjects can and can't be discussed, that person has power over others.
<Side Note For Logic Buffs>
Relevance as a specific subject in discourse and logic first came to my attention in high school. At the time I was fascinated by symbolic logic (oh, there's a shock), and came across the book Entailment: The Logic of Relevance and Necessity by Anderson and Belnap.
<For those annoyed at time lag between volumes of books>
Volume I published in 1975.
Volume II in 1992.
</For those annoyed at time lag between volumes of books>
The book tried to formalize the concept that reasoning required relevance between premises and conclusions, a concept that had been lacking in formal logic.
Here's a summary of the subject:
It's difficult to abstract the concept of relevance, but once done it becomes possible to map the incompatibilities in people's arguments.
</Side Note For Logic Buffs>