St Justin Popovich: True knowledge—“the revelation of the mysteries”...

True knowledge—“the revelation of the mysteries” —is attained by means of the virtues, and this is “the knowledge that saves.”

The chief characteristic—and “proof”—of this knowledge is humility. When the intellect “abides in the realm of knowledge of the truth,” then all questioning ceases, and a great calm and peace descend upon it.

This peace of mind is called “perfect health.” 
When the power of the Holy Spirit enters into the soul, then the soul “learns through the Spirit.”

St Justin Popovich