Sometimes I find myself making an apology in the following form: “Sorry, but I assumed…”. I’ve occasionally been upbraided for this with a response like “Well, you shouldn’t have assumed in the first place, you should have asked.”. There is perhaps something reasonable here—it isn’t good to be presumptuous, and it isn’t good to offer a glossed apology—but, I usually leave such an encounter with a feeling of “Well, that all sounds very reasonable, but in practice we can’t go around constantly questioning and digging into every detail of an interaction; at some point we have to make a pragmatic choice to use background knowledge and assumptions built on our knowledge of social rules and norms, the particular person, and the particular situation.”
Then I realised. When A says to B “I’m sorry, but I assumed…” it is actually a subtle upbraiding of B by A. The less polite version of this is A saying to be “Sorry, but I perfectly reasonably assumed that we were working in our regular framework of norms of communication and our mutual knowledge of each other and the situation, and you unreasonably did something that didn’t fit into those norms and now you seem to be blaming me for making a perfectly reasonable assumption rather than what should have happened which is that you were doing something that was socially or individually uncharacteristic and so you should have proactively given me reasonable information so that I could understand the situation in which we were interacting (innit).”. Of course, this is complicated—one of the reasons that these misunderstandings occur is when A and B think that they are on common ground (what Wittgenstein calls “agreement not in opinions, but rather in form of life”), but actually are working with a different framework.