Sir Isaac Newton gave the extraterrestrials their biggest shot in the arm when he embraced the infinite universe as the basis for his hugely influential system of physics. Even so, the aliens of the early modern period remained creatures of philosophy rather than science.

Like many of the ideas that mattered in the American Revolution, extraterrestrials got their start in antiquity. The Greek philosopher Epicurus speculated that the universe must be infinite, eternal and abounding in 'worlds' just like our own.

We are all equal not because we partake in some peculiar nature or because we share in the same credo of unreasoned beliefs, but because we take it that no thinking being is incapable of seeing reason.

Matthew Stewart Quotes