The Quran repeatedly invites people to look at the alternation of night and day, the rain that revives dead land, the creation of the human being and the stars, as signs for people who think. It does not ask for blind belief: it asks for reflection. Muslim philosophers developed arguments such as the argument from the beginning of the universe and from contingency, which later influenced European thinkers.
Muslims also say that God is known through experience: through prayer, relief after a hardship and the peace that comes from remembering Him. Proof is of different kinds and may not satisfy someone who has decided in advance. Muslims invite honest seekers to ask the questions, read the Quran and ask God sincerely for guidance.