Thanks for these great lessons, as always. A question on one of your examples: why would you say “Моя мама не может обойтись без календаря под рукой” instead of “Моя мама не может обходиться без календаря под рукой"? Aren’t we talking about something general here? In general, my mom can’t get by without a calendar, which I would have thought would call for the imperfective. Is there a nuance that обойтись captures that I’m not understanding? Thanks!

Don responds: Figuring out what aspect of the infinitive to use is tricky. In this context my native-speaker friends say only the perfective works. I generally use the following rule of thumb with infintives: use perfective unless you have a clear idea why you should use imperfective.

In this instance I think the issue has to do with the “relevant result” meaning of the perfective. Обойтись in this context means “to make do,” and making do with or without is a result. The generality of the situation is taken care of by the present tense of мочь, and the result part is taken care of by the perfective of обойтись.

That’s my guess on this one, but frankly aspect is one of the bits of Russian that we as foreigners continually have to work on practically forever. This would drive me into utter despair if it weren’t for the fact that Russians have the same problem in English with a/an/the, so perhaps there is some justice in the world.