The Rambam, the great philosopher and jurist, is commonly understood as being the proponent of an intellectual/rational/deduction-based Judaism as opposed to Rabbi Yehudah Halevi (author of the Kuzari) who used an emotional/mystical/revelation model. However, if you look close enough, you can see that Judaism recognizes a combination of intellectual inquiry and belief in revelation.

In a section of his comprehensive collection of Jewish law, the Rambam describes in fascinating detail how mankind moved from a belief in the one G-d that Adam and others believed in and spoke with at the beginning of Creation, to worshiping idols made out of clay. He paints a picture of a chain of misunderstandings, power struggles and lies.

If you look close enough, you can see that Judaism recognizes a combination of intellectual inquiry and belief in revelation

The Rambam then recounts Abraham’s rediscovery of monotheism by use of his intellect and reason, and the establishment of a community that worshipped one G-d. However, that was not the happy ending. The Rambam concludes with “Abraham’s descendants moved into Egypt and began to lose their pure monotheism and revert to idolatry. When all seemed to be lost, G-d in His love sent us Moses the Prophet and G-d chose the Jewish People as His inheritance and instructed them how to serve Him.”

The Rambam’s long digression into the history of religion has a purpose: it is to tell us that yes, G-d can be known and discovered solely through the intellect, but only by a select few. For the rest of us, intellect alone is not enough, as we all know how easy it is to intellectually justify any behavior (with or without creating an alternative belief system) if we want to badly enough. This is why we must first base ourselves on the Divine Revelation at Sinai, and only then we can use our intellect to know G-d.