EQUIVALENCE: P ≡ SOMEONE KNOWS THAT P

jurij Derenikovič has devoted very much time and, as always, fruitful work to a certain important part of verbal semantics, viz. to the concept know / Russian znat’. For many decades now he has insisted on its primitive character. We find a new exposition of this idea in [Apresyan 2018] where a large number of other epistemic expressions are scrutinized as well. While his view of the concept of knowledge is not identical with mine in all its details, I share with him the basic non-conventional attitude concerning the widely debated issue of definability of ‘knowledge’ and ways of defining it. I myself have spent much time arguing for the treatment of the fundamental expression ‘someone knows about _ that _, not: _’ as simple, i.e. indefinable, and universal [cf., in particular: Bogusławski 1981].