Chazal teach that the six thousand years of the world's existence is divided into three sets of two thousand years. The first two thousand were years of תהו - emptiness - spiritual desolateness. During that time the world at large was ignorant of Hashem's Presence and worshipped various idols. Next, came two thousand years of Torah. This, Chazal tell us, began during the days of Avraham Avinu.
(עבודה זרה ט.)
Furthermore, the Midrash tells us that the pasuk in Parshas Bereishis "ויהי אור" - and there was light, which literally refers to the creation of light, alludes to Avraham Avinu. By announcing Hashem's Name to humanity, he caused the world to be filled with a special, Divine Light.
(מדרש רבה בראשית פרשה ב אות ג)