"The frame of nature, and the system of the world, we are to observe by the phenomena, and not to frame by imagination."

"The changing of bodies into light, and light into bodies, is very conformable to the course of nature, which seems delighted with transmutations."

"The particles of light are exceedingly small, and move with exceeding swiftness."

"I do not define time, space, place, and motion, as being well known to all."

"He who thinks half-heartedly will not believe in God; but he who thinks seriously will believe in God."