It hasn't come up much in game, but I tried to base the religious system in my world on a sort of neoplatonic system. The classical Greek gods exist, but they are merely reflections of some deeper truth.

Souls pass through a cycle of reincarnation. The conventional view is that you retain knowledge in some form between lives. This is why, with some prompting, people can often figure out basic things like certain mathematical formulas on their own. This also includes philosophical learning. It is thought that those who study philosophy in a previous life can come to a deeper understanding in their next. Over many cycles of death and rebirth you will come to a true understanding of the nature of the universe.

Philosophy plays an important part in the setting. Philosophical academies take the place of monasteries, and some of the treasure the party has found were ancient philosophical texts, thought lost to history.

I also have an idea about using my vague understanding of Aristotelian physics to do a trip to the moon type game. Everything has a natural place in the universe. Earth type materials fall towards the center of the earth, moon type materials fall towards the center of the moon. But, through the marvels of modern alchemy enough selenium has been produced to construct a vessel capable of taking a mission to the moon. Now, of course you can't build the entire thing out of selenium, so the vessel will have to start its voyage being fired out of a cannon to escape the Earth's influence.