If our own thinking determines, or at least has a part in shaping the reality we live in, that is, in determining the nature of that reality, and is not just a sub-function of a pre-existing reality; if it is possible that we have a part in shaping reality, then there is no stronger argument for pursuing a spiritual life, a life of purpose and meaning, a religious life. Pursuing a religious life means choosing a trajectory towards the good, towards justice and morality, towards Adonai/God. This means that inwardly thru our beliefs and thoughts, and outwardly thru our acts of compassion, justice, and creativity, we are trying to build a human reality that reflects the Jewish conception of Adonai. But tho this conception is quintessentially Jewish, its fulfillment is in no way limited to Jews.
If we accept such a possibility and choose to pursue it, then faith alone is not sufficient. Nor are good works alone sufficient. If we are creating this reality through our thoughts as well as our deeds, then both our beliefs and our actions are critically important. Thus, to reject God or exclude God from our conceptions is to pursue an incomplete, broken, and ultimately dysfunctional model. Without God, one is inevitably left with the Machiavellian/Darwinian world of blind and random nature, devoid of any inherent ethics, justice, and purpose.
[A note on atheism:] While it is undeniable that one can be deeply and consistently ethical without actively believing in God, consistent ethical behavior (as opposed to situational, self-serving ethical behavior) ultimately rests on a belief in values that transcend personal needs and personal gain. And to believe in such “transcendental” values ultimately means our inner logic is founded on some sort of God idea. Many ethical atheists prefer not to pursue the logic of their beliefs, but in the end their atheism really rests on a religious, God-based foundation. Ideas such as “for the good of society” or “for the good of humankind” or “for the good of the earth” are all ways of submerging God into one’s beliefs without having to acknowledge God.