Beginning soon after the turn of the 20th century, four influential Latter-day Saint scholars began to systematize, modernize, and codify Mormon doctrine: B. H. Roberts, James E. Talmage, John A. Widtsoe, and Joseph Fielding Smith. In 1921, the church called chemistry professor John A. Widtsoe as an apostle. Widtsoe's writings, particularly "Rational theology" and "Joseph Smith as Scientist", reflected the optimistic faith in science and technology that was pervasive at the time in American life. According to Widtsoe, all Mormon theology could be reconciled within a rational, positivist framework.