Throughout much of history, the Jewish way of life has been characterized by strict adherence to the practices and prohibitions legislated by the Torah. These rules eventually came to regulate all aspects of Jewish life, from morning until night and from cradle to grave. But precisely when did this unique way of life first emerge, and why specifically at that time? This study methodically engages ancient texts and archaeological discoveries to reveal the earliest evidence of Torah observance among ordinary Judeans. A litany of elements characterising Judaism are examined: the dietary laws; the ritual purity rules; a ban on figural art; tefillin and mezuzot; circumcision; the Sabbath prohibitions; the Passover sacrifice and the Festival of Unleavened Bread; fasting on the Day of Atonement; the central rituals of the Sukkot festival; and the temple menorah. Also examined is the emergence of the synagogue as an institution dedicated to the public dissemination of the Torah. This detailed examination reveals that we possess no compelling evidence dating to any time prior to the middle of the second century BCE which suggests that the Judean masses knew of the Torah and were observing its laws in practice. To explain these results, the book seeks the genesis and earliest development of Judaism either during the Early Hellenistic period, when Judea found itself under foreign domination by the two great Hellenistic kingdoms, or during the Late Hellenistic period, after the Judeans had gained autonomy under the leadership of the priestly Hasmonean family.