We know from several midrashim (see first chapter of Midrash Tanchuma to Bereshit) that Torah had already existed before the world was created. It should have contained all the positive and negative commandments, and the latter assumes the knowledge of the evil.
Sifrei (p. 4 left column in this edition) mentions that Adam was to study and keep commandments, while Bereshit Rabbah (p. 130/178 in the translation) writes that he was to offer sacrifices. This means that he was obliged to study at least about certain positive commandments.
But what was the purpose of Hashem with Adam and Eve regarding Torah study of the negative commandments if they were not allowed to eat from the tree of the knowledge of good and evil? Besides the introduction of the evil inclination, Rashi also comments on 2:25 that before eating from the fruit they were simply unable to tell the good and the bad apart. However, Sanhedrin 56b and Bereshit Rabbah (p. 131/179) explicitly tell us that they were forbidden to do idolatry and blasphemy, curse judges, shed blood, do sexual immorality, steal and eat limbs of living animals (i.e. the Noachide laws). How did they know the meaning of these concepts? How could they know that these things were bad?
