[On the history of the idea of life in the Universe: the age of Enlightenment (Fontenelle, Huygens, Kant). In commemoration of the three hundredth anniversary of the death of Christiaan Huygens (1629-1695)].

The idea of the plurality of worlds, and moreover, worlds inhabited by living beings, which nowadays carries so much theoretical and practical significance, did not originate only with the advent of the Enlightenment. On the contrary, its history goes back for centuries and it may be said, without much exaggeration, to be as old as philosophy itself. However, the Age of Enlightenment constitutes a special period for the history of this idea at least for two reasons: firstly, because of the fact that the process of transformation of the idea from a philosophical into a scientific one, which began in 17th century, reached its conclusion in that period, and secondly, because it was in that period that the idea of the plurality of inhabited worlds came into the foreground for the first time. Thus the abstract problem of the plurality of worlds came to be replaced at the beginning of the 18th century by the imagination-rousing idea of life in the Universe. During the Enlightenment period, the idea discussed in this article gained an unprecedentedly wide currency, as it left the pages of philosophical and scientific treatises, in order to be reflected in didactic poems, which disseminated it even further....