Correlative with I was unknown, Gal 1:22. Note the periphrasis of the participle with the substantive verb, expressing duration. They were hearing all the time that I was thus unknown to them in person.
The faith
See on Act 6:7, and comp. 2Th 3:2. The subjective conception of faith as trustful and assured acceptance of Jesus Christ as Savior, tends to become objective, so that the subjective principle is sometimes regarded objectively. This is very striking in the Pastoral Epistles.