We should never say, "I already know that Hashem created the world. I don't need to keep studying it; I'm a maamin (believer) without that."
We need to continually increase our Emunah Chushis (belief that is built on physical sensory perception). If a person has the opportunity to see the wonders of Hashem's Creation with his own eyes and he doesn't want to do it, he is revealing that he is lazy in avodas (the service of) Hashem. -- Ohr Avigdor Shaar Bechina.