In a really well-done video for the Ex-Muslims of North America, we learn about Muhammad ibn Zakariya al-Razi. Al-Razi who lived over a millennium ago, was a physician, philosopher, and astronomer. His work was tremendously influential in western medicine.
And there’s reason to believe he rejected organized religion. As the video says, he’s “Islam’s favorite heretic.”
Because he lived so long ago, there’s some question as to how non-religious he was, but there’s virtually no doubt about his influence and legacy. He succeeded by relying on reason over religion.