The Nyaya School Responds to Skeptical Attacks

Nyaya accepts that there are two types of sources of knowledge. One is known first and then it operates towards his object but the other one even not known operates towards its object. So in Sanskrit we say Nyaatamsat, promana, mavati something is a source of knowledge when it is already known. This premise itself is faulty or defective can I say so that the accusation does not stand at all because for Prataktakshapramana we do not need. That the source of knowledge must be known prior to the operation.