Every rare once in a while, I find myself caught in a conversation where the person I'm talking to goes off on a tangent. And I don't mean a little aside. I mean a "What the hell are you talking about!?" tangent.
Luckily, for the other 99% of conversations, there are some general guidelines for engagement that help us avoid making mistakes like this one. H. Paul Grice, a language philosopher, is the scholar credited with first writing about these rules in a widespread way. Grice theorized that participants in conversation operate by an overarching approach that we now call The Cooperative Principle.
Bramlett, Frank, "So What's Your Point? Relevancy in Conversation" (2003). English Faculty Publications. 39.