While Briggs held to traditional Christian teaching in many areas, such as his belief in the virgin birth of Jesus, conservatives were alarmed by his assertion that doctrines were historical constructs that had to change over time. He did not believe that the Pentateuch was authored by Moses or that the book of Isaiah had a single author. In addition, he also denied that Biblical prophecy was a precise prediction of the future. In 1891, Briggs preached a sermon in which he claimed the Bible contained errors, a position many in the church considered contrary to the Westminster Confession's doctrines of verbal inspiration and Biblical inerrancy.