Greco-Roman Period
Lawrence H. Schiffman, From Text to Tradition, Ktav Publishing House, Hoboken, NJ, 1991.

In tannaitic literature, two terms are employed which signified two aspects of the emerging tradition, halakhah and aggadah. The word halakhah was used to denote Jewish law as it was understood and determined by the tannaim and later by the amoraim. This term has been explained in two ways. Many have seen it as emerging from the root hlk, “to go,” metaphorically suggesting the concept “a way of life.” Another view derives the
word halakhah from an ancient Mesopotamian tax on land called ilku in Akkadian, and halakh in biblical Aramaic.

In contrast, the second category, aggadah, known also as haggadah (a term later used to denote the Passover Seder text) is that part of rabbinic teaching not considered obligatory. Aggadah, derived from the verb higgid (from the root ngd) meaning “to tell,” consists of interpretations, stories, and legends, all of which are designed to attract followers to Rabbinic Judaism and to explicate its teachings and principles. Since in many areas the aggadah provides differing positions on the same issues, no one position can be obligatory. Originally, this was also the case with halakhah, but a long process of decision-making eventually resulted in a normative set of laws by the Middle Ages. The practical aspects of the need to determine the authoritative ruling led more and more toward standardization. Such a process never occurred in regard to the non-legal aspects of rabbinic tradition, the aggadah. Hence, aggadah continued to demonstrate greater variety than did halakhah.

These two aspects of talmudic tradition demonstrate the creative tension in Rabbinic Judaism between the fixed and the flexible. The fixed body of law and practice is offset by the more open and nonobligatory teachings regarding which the rabbinic Jew is free to disagree. This characteristic is an important principle in the later development of traditional Judaism, since it allowed the eventual standardization of most of the halakhic norms while leaving open to debate the theological underpinnings, all within certain limits which emerged from the rabbinic consensus at the end of the talmudic period.