Fitch's Paradox of Knowability and Ramified Theory of Types

It is already known that Fitch's knowability paradox can be solved by typing knowledge within ramified theory of types. One of the aims of this paper is to provide a greater defence of the approach against recently raised criticism. My second goal is to make a sufficient support for an assumption which is needed for this particular application of typing knowledge but which is not inherent to ramified theory of types as such.