St Nikolai Velimirovich and the Doctrine of Causality

[Isaac the Idiot]

St Nikolai defends the Orthodox doctrine of personal causality in this article. It has been suggested to me that he is wrong . St Nikolai does not provide any references to his sources in Tradition and the Lives of the Saints - does anyone know where one would look to find out more about the true Orthodox approach to this subject? (I'm inclined to believe that St Nikolai has already given us the answer, but in the face of criticism, some other evidence would be greatly appreciated).