Liberal infection of conservative causes

The quote below is from someone who back in the day would be sold to us as a conservative evangelical safe to follow.

There is, then, no absolute proof that our Canon is precisely the true Canon and no absolute proof that any one word of the text is precisely as God gave it. But the quest for absolute proofs, whether historical or theological, is based on a misunderstanding of the nature of history, theology, and the human mind. History is at best an approximation to truth based on an incomplete induction of facts. Theology is a fallible human attempt to co-ordinate the data of revelation.

Christ and the Bible, John William Wenham. London, Tyndale Press, 1972, p. 184.