The End of the Contemplator Caeli

Many Greek and Roman philosophers cherished the ideal of the contemplator coeli, according to which human beings were meant to observe the sky and nature as a whole. In this ideal, the human eye and nature were teleologically optimized for each other so that humans could see all that was allowed them by gods or God. Hans Blumenberg labelled this openness of nature to human sight as the ‘postulate of visibility’. When early modern natural philosophers and astronomers started to use telescopes and microscopes for the investigation of nature, the ideal of the contemplator coeli vanished. Both types of instruments invalidated the notion that human senses naturally captured the constitutive elements of nature. Looking through telescopes and microscopes had serious epistemological consequences: It became clear that nature contained an inexhaustible number of invisible objects. Philosophers also realized that humans saw only the surface of reality, behind which lay the immeasurable dimensions of other layers of reality in the microworld and the macroworld. Telescopes and microscopes thus demonstrated that human knowledge had a tiny range and depth relative to nature. By the end of the seventeenth century, however, the limits of human knowledge were no longer perceived as an epistemological fatality but as a horizon for further expansion and development.