The deceitfulness of the heart of man appears in no one...

The deceitfulness of the heart of man appears in no one thing so much as this of spiritual pride and self-righteousness. The subtlety of Satan appears in its height, in his managing persons with respect to this sin. And perhaps one reason may be that here he has most experience; he knows the way of its coming in; he is acquainted with the secret springs of it: it was his own sin. Experience gives vast advantage in leading souls, either in good or evil.