Habitual action creates expectations (especially in informal contexts, like interactions between family members). This is a perfectly ordinary thing. If (as you suggest at the start of the comment) Bob also understands this fact, then there’s nothing unusual here at all; Bob has created an expectation that he’ll be coming on Friday, and he knows this, and he then violates this expectation. This is a betrayal, especially given that it’s his mother we’re talking about, and given (as you say) that this matters to her (and that Bob knows this, too).
Now, the expectation isn’t very firm, and the betrayal isn’t very severe. Like I said before, there are degrees of this thing. But the situation isn’t of a different kind. So why call Alice’s feelings irrational?
It seems to me that this isn’t at all an example of the given extensional definition.
Habitual action creates expectations (especially in informal contexts, like interactions between family members). This is a perfectly ordinary thing. If (as you suggest at the start of the comment) Bob also understands this fact, then there’s nothing unusual here at all; Bob has created an expectation that he’ll be coming on Friday, and he knows this, and he then violates this expectation. This is a betrayal, especially given that it’s his mother we’re talking about, and given (as you say) that this matters to her (and that Bob knows this, too).
Now, the expectation isn’t very firm, and the betrayal isn’t very severe. Like I said before, there are degrees of this thing. But the situation isn’t of a different kind. So why call Alice’s feelings irrational?
It seems to me that this isn’t at all an example of the given extensional definition.