How would I express my ability not to do something?
"I cannot dig" means that I definitely cannot dig. But how do I express my ability not to dig? The first thing that comes to my mind is "I am able not to dig", but I was wondering if there was a better way to express that.
In essence I want to say something like "I can (not dig)"; parentheses are just for clarification.
UPDATE
Ok, so in order to clear things up, I tried to think of a better example. Lets imagine that I am walking in the park and see some big guy bullying a nerd. In this case I would like to say "I am able not to interfere, but I will!" (or in our case what I would like to say is "I can (not interfere), but I will!").
And someone working in the circus might want to say "I can (not fall) while walking on a narrow plank".
And the main question is – is it possible to express those examples using "can"?
Best Answer
The usual idiom is "I don't have to dig".
In speech it is possible to express "I can (not dig)" by intonation, but there is no customary way to manage that in writing. *
Edit in response to the edits to the question: in those cases where you really are talking about the ability not to, as opposed to the lack of obligation: no, you will need to use a perphrasis, probably "able not to", as in your example. There isn't an unambiguous way of using "can" for this meaning.
Slightly off topic: the scope of negation can vary a lot between different languages. English "must not" ("obliged not to") is not a translation of German "muss nicht" ("permitted not to").