The historical value of talmudic texts is a contested issue in modern talmudic studies. Historians regularly utilize legal differences between the Talmuds of Palestine (edited c. 370 C.E.) and Babylonian (edited c. 650 C.E.) to assist in the reconstruction of Jewish history in the two centers. However, while some halakhic differences may be the result of external influences (cultural or regional differences between Persian Babylon and Roman or Byzantine Palestine) others are the product of internal factors (textual, hermeneutical, and dialectical). In her important study, Christine Hayes critiques a historical approach that posits external explanations for divergences between the two Talmuds without paying sufficient attention to internal factors. Hayes demonstrates through a careful analysis of parallel passages from Bavli and Yerushalmi Avodah Zarah, that textual, hermeneutical, and dialectical factors frequently generate halakhic difference between the Talmuds. Nonetheless, Hayes argues that under certain conditions halakhic difference can provide information of use to the historian. A second set of case studies reveals that it is precisely when the Talmuds violate standard strategies of interpretation and argumentation that external (historical) factors are the likely cause of the halakhic difference in question. She thus shows that our knowledge of the different characters of the two Talmuds and their particular hermeneutical and dialectical practices acts not only as a brake on inappropriate historical analysis but also as a guide to appropriate historical analysis.