Belief in God is rational. Everything has a cause. So unless there is a first cause, then you would have an infinite regress. And then nothing could exist. Therefore there must be a first cause. Therefore God, the first cause, exists. QED.
11.4.12
I want to introduce a new type of Judaism that already many people keep but don't know that it is in fact a new branch. It's called "shomer mitvot" i.e. keeping the 613 mitzvot. This is different than Reform which does not hold from mitzvot. This is different than Orthodox which makes up mitzvot at random and ignores all real mitzvot. The importance of mitvot is that this is the actual idea of Torah of what is important.