In the book, we present to the Czech reader the work of the French philosopher Bernard de Fontenelle, which is entitled Conversations on the Plurality of Worlds". The book is considered one of the first works aimed at popularizing science. Fontenelle describes the cosmological theory of René Descartes by means of interviews between an inquisitive marquise and a learned philosopher. Among other things, Fontenelle is one of the first to consistently conceive of the existence of extraterrestrial life. The translation of the dialogue is accompanied by a comprehensive introductory study that puts Fontenelle's reflections in the contemporary philosophical and scientific context.