Learn Turkish: Doğaüstü bir güç bu mağarayı kazmış olamaz. - A supernatural power cannot have dug this cave.

This is the negative epistemic past deduction taught in this lesson. It combines the past participle kazmış (having dug) with the negative potential aorist auxiliary olamaz (cannot be). Literally, it means it cannot be a case of having dug. We use this structure to express a strong logical deduction or complete disbelief about a past event.

What is the difference in meaning between kazmış olamaz and kazmamış olmalı?

Kazmamış olmalı means must not have dug (I deduce that it didn't happen), using the negative past participle with the necessity suffix. Kazmış olamaz means cannot have dug (it is physically or logically impossible that it happened), using the positive past participle with the negative potential auxiliary. The latter expresses a much stronger sense of disbelief.

How is the compound word doğaüstü formed?

It is a noun compound functioning as an adjective, made from doğa (nature) and üst (top, above). The -ü at the end is the compound marker (the third-person possessive suffix). Literally meaning nature's above, it translates to supernatural. In Turkish, established abstract compounds like this are usually written as a single word.

Why does mağara take the accusative suffix -yı here?