The complement to the Spirit's witness — the believer's own conscience, rightly informed by the gospel, testifying that they walk in love and holiness. Both witnesses go together.
Sermon 12 of 44 · 1746 · 2 Corinthians 1:12
The Witness of Our Own Spirit
A passage from the sermon
The testimony of our own spirit is no other than the testimony of our conscience: even of our conscience now made sensible of God's mercy, and now bearing witness with the Holy Spirit that we love God, and serve him with all our might. This is what St. Paul calls 'the answer of a good conscience toward God.'
Let no one rest in either witness alone. The Holy Spirit's witness, without the fruits of the Spirit in heart and life, is a deception. The witness of our own spirit, without the immediate testimony of God's Spirit, is a building without a foundation. But where both go together — there is the full assurance of faith.
The full sermon is in the public domain and freely available from CCEL and other archives.