On the Infinite Universe and Worlds

A work of five dialogues in Italian, written and printed in London in 1584 while Bruno was living in the household of the French ambassador. Its spokesman, Filoteo, argues against the closed cosmos of Aristotle and the medieval astronomers. Space is infinite and has no centre and no outer sphere. An infinite God, whose power and goodness have no limit, would produce an infinite effect, not a bounded world. The universe therefore contains countless worlds: the fixed stars are suns, and they have planets of their own, some of which may be inhabited. Bruno takes up Copernicus's moving earth but goes much further, removing the sun as well as the earth from the centre of everything. Interlocutors raise the standard objections, and in the final dialogue Albertino presents Aristotle's arguments for a finite universe one by one, only to be answered and won over. Bruno was later tried by the Roman Inquisition and burned in 1600, chiefly on theological charges.

It is one of the first full arguments for an infinite universe with countless suns and planets, and it shows how metaphysics and theology drove early modern cosmology as much as observation did.