Since you paint them with a broad brush, you ought to be able to present lots of in-context citations backing up this remarkable claim.
But really ... the only source of truth??
So God himself is demoted, and is not a source of truth?
So the church founded by God, which St Paul calls directly, "the pillar and ground of the truth," is not a source of truth?
So creation, which Scripture teaches in several places testifies to God's glory and his law, so that even the Gentiles are "without excuse," is not a source of truth?
Man's right reason, created by God to glorify him, is not a source of truth?
I'm pretty sure that none of the early fathers embraced a notion so manifestly false and contrary to Scripture.
Whatever are you talking about? God Himself wrote the scriptures through men inspired by the Spirit. That is the ONLY source of truth by which we measure everything.
Man's right reason, created by God to glorify him, is not a source of truth?
Man doesn't have a "right reason". No one seeks after God-no, not one. Our hearts are wicked and deceitful in which we are cautioned to guard against. Now if you want to tell me that Aunt Agnes talked to God. And you're confident that she's a good source because she's a pretty nice lady who bakes cookies for the home groups, then perhaps we'll need to talk about this in more detail.
I'm pretty sure that none of the early fathers embraced a notion so manifestly false and contrary to Scripture.
I suggest you re-examine this notion. That is precisely why we have the Bible.