The Conferences Of John Cassian by John Cassian
Chapter XIV. A question how such wrong notions can creep into us.
Germanus: Very aptly has your discussion shown the error of these illusions by this illustration: but we should like in the same way to be taught its origin and how to cure it, and we are equally anxious to learn how this deception has taken hold of us. For everybody must see that no one at all can apply remedies to ill health except one who has already diagnosed the actual origin of the disease.