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.
19.1.21
Gra who is classified as a rishon
The climatic end of the Rishonim was the Gra who is classified as a rishon but yet comes later as a sort of seal on the period. And the significant thing about the Gra was the purity. He defines what Torah is about--even for us folks that are not on that level to fulfill any or even most of the details. That is why I recommend having a yeshiva on the name of the Gra in every city. This would have the benefit that even us common folk can have an idea of true and authentic Torah is about, even if we are not up to that level of being able to fulfill it.