On the Heavens (Greek: Περὶ οὐρανοῦ, Latin: De Caelo or De Caelo et Mundo) is Aristotle's chief cosmological treatise: written in 350 BC it contains his astronomical theory and his ideas on the concrete workings of the terrestrial world. It should not be confused with the spurious work On the Universe (De mundo, also known as On the Cosmos).
According to Aristotle in On the Heavens, the heavenly bodies are the most perfect realities, (or "substances"), whose motions are ruled by principles other than those of bodies in the sublunary sphere. The latter are composed of one or all of the four classical elements (earth, water, air, fire) and are perishable; but the matter the heavens are made of is imperishable aether, so they are not subject to generation and corruption. Hence their motions are eternal and perfect, and the perfect motion is the circular one, which, unlike the earthly up-and down-ward locomotions, can last eternally selfsame. The beginning of this motion was referred to by Aristotle as the Unmoved Mover, his supposition for a supernatural metaphysical entity. As substances, celestial bodies have matter (aether) and a form: it seems that Aristotle did regard them as living beings with a rational soul as their form  (see also Metaphysics, bk. XII) This work is significant as one of the defining pillars of the Aristotelian worldview, a school of philosophy that dominated intellectual thinking for almost two millennia. Similarly, this work and others by Aristotle were important seminal works by which much of scholasticism was derived.
Aristotelian philosophy and cosmology was influential in the Islamic world, where his ideas were taken up by the Falsafa school of philosophy throughout the later half of the first millennia AD. Of these, philosophers Averroes and Avicenna are especially notable. Averroes in particular wrote extensively about On The Heavens, trying for some time to reconcile the various themes of Aristotelian philosophy, such as natural movement of the elements and the concept of planetary spheres centered around the Earth, with the mathematics of Ptolemy. These ideas would remain central to the philosophical thinking of that culture until the rise to prominence of Al-Ghazali, a philosopher and theologian who argued against Aristotelianism and neoplatonism during the 12th century.
European philosophers had a similarly complex relationship with De Caelo, with repeated attempts to reconcile the mathematics of Ptolemy with the structure of Aristotle. A particularly cogent example of this is in the work of Thomas Aquinas, theologian, philosopher and writer of the 13th century. Known today as St. Thomas of the Catholic Church, Aquinas worked to synthesize Aristotle's cosmology as presented in De Caelo with Christian doctrine, an endeavor that led him to reclassify Aristotle's prime movers as angels, attributing the 'first cause' of motion in the celestial spheres to them. Otherwise, Aquinas accepted Aristotle's explanation of the physical world, including his cosmology and physics.
De Caelo surfaced again during the 14th century by the hand of French philosopher Nicole Oresme, in his role as advisor to King Charles V of France. He translated and commentated on De Caelo on two separate occasions, once early on in life, and again near the end of it. Respectively, the versions were a traditional Latin transcription and a more comprehensive French version that synthesized his views on cosmological philosophy in its entirety, Questiones Super de Celo and Livre du ciel et du monde respectively. "Livre du ciel et du monde" was written at the command of King Charles V, though for what purpose remains of some debate. Some speculate that, having already had Oresme translate Aristotelian works on ethics and politics in the hope of educating his courtiers, doing the same with De Caelo may be of some value to the king.
(in reverse chronological order)
- Stuart Leggatt, On the Heavens I and II (Warminster: Aris & Phillips, 1995). ISBN 0-85668-663-8
- William Keith Chambers Guthrie, Aristotle On the Heavens (Cambridge, Mass.: Harvard University Press "Loeb Classical Library", 1939).
- John Leofric Stocks, On the Heavens (Oxford: Clarendon Press, 1922).
- Adelaide Etexts
- Sacred Texts
- MIT (incomplete)
- Internet Archive (Scanned Version of Printed Text)
- Audiobook (Public Domain / Internet Archive)
- Thomas Taylor, The treatises of Aristotle, on the heavens, on generation & corruption, and on meteors (Somerset, England : The Prometheus Trust, 2004, 1807). ISBN 1-898910-24-3
- Dalimier, C. and Pellegrin, P. (2004) Aristote. Traité du ciel (Paris).
- Moraux, P. (1965) Aristote. Du ciel (Paris).
- Tricot, J. (1949) Aristote. Traité du ciel. Traduction et notes (Paris).
- Gigon, O. (1950) Vom Himmel, Von der Seele, Von der Dichtkunst (Zurich).
- Prantl, C. (1857) Aristoteles’ Vier Bücher über das Himmelsgebäude und Zwei Bücher über Entstehen und Vergehen (Leipzig).
- Prantl, C., (1881) De coelo, et de generatione et corruptione (Leipzig).
- Jori, A., (2008), Über den Himmel (Berlin).
- Jori, A. (1999) Il cielo (Milan).
- Longo, O. (1961) Aristotele. De caelo (Florence).
- "On the Heavens" in Greek is found in the 2nd volume of the 11-volume 1837 Bekker edition of Aristotle's Works in Greek (DJVU)
- Elders, L., Aristotle’s Cosmology: A Commentary on the De Caelo (Assen, Netherlands: Van Gorcum, 1966).