The First Step Astray...

"The first step astray is a want of adequate faith in the divine inspiration of the sacred Scriptures. All the while a man bows to the authority of God's Word, he will not entertain any sentiment contrary to its teaching. "To the law and to the testimony," is his appeal concerning every doctrine. He esteems that holy Book, concerning all things, to be right, and therefore he hates every false way. But let a man question, or entertain low views of the inspiration and authority of the Bible, and he is without chart to guide him, and without anchor to hold him.
In looking carefully over the history of the times, and the movement of the times, of which we have written briefly, this fact is apparent: that where ministers and Christian churches have held fast to the truth that the Holy Scriptures have been given by God as an authoritative and infallible rule of faith and practice, they have never wandered very seriously out of the right way. But when, on the other hand, reason has been exalted above revelation, and made the exponent of revelation, all kinds of errors and mischiefs have been the result."
Robert Schindler, "The Down Grade," (second article) The Sword and the Trowel (April 1887), 166.

Spurgeon and the Down-Grade Controversy by John MacArthur