and the sublunar spheres, from an engraving of
Albertus Magnus'
Philosophia naturalis Plato and
Aristotle helped to formulate the original theory of a sublunary sphere in antiquity, the idea usually going hand in hand with
geocentrism and the concept of a
spherical Earth.
Avicenna carried forward into the Middle Ages the Aristotelian idea of generation and corruption being limited to the sublunary sphere.
Medieval scholastics like
Thomas Aquinas, who charted the division between celestial and sublunary spheres in his work
Summa Theologica, also drew on
Cicero and
Lucan for an awareness of the great frontier between Nature and Sky, sublunary and aetheric spheres. The result for medieval/Renaissance mentalities was a pervasive awareness of the existence, at the Moon, of what
C. S. Lewis called "this 'great divide' ... from aether to air, from 'heaven' to 'nature', from the realm of gods (or angels) to that of daemons, from the realm of necessity to that of contingence, from the incorruptible to the corruptible". However, the theories of
Copernicus began to challenge the sublunary/aether distinction. In their wake,
Tycho Brahe's observations of a new star (nova) and of comets in the supposedly unchanging heavens further undermined the Aristotelian view.
Thomas Kuhn saw scientists' new ability to see change in the 'incorruptible' heavens as a classic example of the new possibilities opened up by a paradigm shift. ==Literary offshoots==