Think that the basic premise here being presented is very flawed in regards to thsoe trying to link calvin and others to Gnostic sources...
John Calvin took his doctrines and teaching prime sourced the holy Bible...
Disagree with how he interpreted them, but do NOT say that he invention something from Gnostic or nothing!
They are trying to say connect the dots.
The dots they have given arre as follows:
Augustine was once a gnostic>because he was once a gnostic gnosticism influenced his views on scripture and the kingdom of God>Augustine influenced Calvin>any doctrine Calvin had was influenced by gnosticism because of augustines influence on him>therefore calvins doctrines are gnostic
It is a formal fallacy.