Midrashim tell how Avraham Avinu deduced at an early age that Hashem was the Creater and Ruler of the world. He tried worshipping the earth, the rain, the sun, the moon, etc. but deduced that not one of these forces regulated the world and that:
There must be a higher intelligence directing them [the various forces].
“I have not seen Him,” said Avram, “but I can understand that only a mighty and merciful G-d could have created the… world around me, and only his superior intelligence is able to keep it going. To Him will I bow.” (The Midrash Says, by Rabbi Moshe Weissman, Sefer Breish’it, Parsha Noach, page 118.)