If you submit everything to reason there will be no mystery and no supernatural element in your religion?

This is a quote by Blaise Pascal from the Pensees (part 4, Note 273) and he is only kind of right (like most of Pascal's thinking). Reason is the ability to understand cause and effect, how one thing leads to another and to be able to distinguish between causation and correlation and science is built upon the principles of reason so would eliminate the "super natural" from religion- There is only that which is understood and that which is not understood, both categories are still "nature" and nature cannot be transcended.

However, there is ALWAYS mystery- There will always be things we as a species don't know as well as things that we as individuals do not know. Additionally, even things which we do know, and even know well, can be the source of awe and retain their elements of poetic mystery: We know why a plant is green but that does nothing to reduce its beauty. We know how architecture is built but does not detract from the sovereignty found in a place like the Taj Mahal.