Many insights in understanding the Bible that began in the nineteenth century continue to be discussed in the twenty-first; in some areas of study, such as linguistic tools, scholars merely appropriate earlier work, while in others they "continue to suppose they can produce something new and better". For example, some modern histories of Israel include historical biblical research from the nineteenth century. In 1835, and again in 1845, theologian Ferdinand Christian Baur postulated the apostles Peter and Paul had an argument that led to a split between them thereby influencing the mode of Christianity that followed. This still occasions widespread debate within topics such as Pauline studies, New Testament Studies, early-church studies, Jewish Law, the theology of grace, and the doctrine of justification. Albrecht Ritschl's challenge to orthodox atonement theory continues to influence Christian thought.