# It is able to be possible/ She is able to have drunk

If "can" and "be able to" are interchangable sometimes, for example:

She can speak Latin = She is able to speak Latin

Can "be able to" be used instead of "can" in:

She can't have drunk that much coffee = She isn't able to have drunk that much coffee

It can be possible that he has forgotten about us = It is able to be possible that he has forgotten about us ?

• Both starting examples use can in a wooly way. Then converting to be able to makes them worser, no, worsted. Commented Jun 5, 2020 at 13:30
• It's some "wool" humor or what? I don't understand Commented Jun 5, 2020 at 14:20
• If "can" and "be able to" are interchangable sometimes, This is your problem. You have chosen times when they are not interchangeable. She can't have drunk... - this uses "can" to express an probability/possibility. The second one does too but it is not really idiomatic. We would say "It could be possible..." When can is used to express a possibility or request permission, its meaning is not "to be able to". Commented Jun 5, 2020 at 14:37
• I was told "It can be possible" was not a good sentence. Using "could" - "Could it be possible" makes everything fine? Commented Jun 5, 2020 at 14:43
• All of those constructions are syntactically sound. The first example is fine, but the second is unidiomatic and awkward. Commented Jun 5, 2020 at 15:31