John Philoponus, Aristotle’s Early Creationist Critic


Author: Dan Graves
Subject: History
Date: 6/24/1998

Article adapted from the Dan Graves’ book, Scientists of Faith

The first to present his case seems right until another comes forward and questions him. Proverbs 18:17.

The power of the creationist view can be better seen at the very outset of Western science in the person of John Philoponus.

Aristotle (384-322 B.C.), the ancient Greek philosopher and scientist whose views still reverberate today, did more than perhaps any other thinker to shape pre-Christian science. But his theories, while innovative for his day, often combined brilliant insights with a good deal of nonsense-nonsense that opposed several fundamental tenets of first Judaism and then Christianity.

Significantly, Aristotle’s most serious critic in the first seven hundred years was John Philoponus, an Alexandrian Christian. In response to Aristotelian error, Philoponus forged a sustained attack against Aristotle’s chief proponent during the seventh century A.D., a Greek philosopher named Simplicius. Fortunately for modern science, Simplicius often responded to those attacks with long quotations from Philoponus, inadvertently preserving his opponent’s work for posterity.

Philoponus’s application of Christian theology to physics prefigured a new era in science. The Alexandrian scholar was the first to combine scientific cosmology (the study of the nature of the universe) with monotheism and the Christian doctrine of creation. In doing so, Philoponus anticipated not only the findings but also the methods of modern science. He controlled his observations in the manner of genuine research, although it is not certain he ever progressed beyond thought experiments-that is, experiments carefully thought out, but not actually performed.

Three fundamental beliefs dominated Philoponus’ thinking:

  • The universe is the single creation of a single God and not eternal
  • The heaven we see has the same physical properties as the earth
  • Stars are not divine

Simple ideas these were, but they had profound implications as to the origin and duration of the universe, its constitution, and its physical forces. If the universe was created, it is not infinite in duration. Aristotle taught that it is. If the universe was created, the heavenly bodies can reasonably be assumed to be of the same material as the rest of creation. Aristotle taught that the stars are made of a special celestial stuff. If the heavenly bodies are material, they must be moving in a void; otherwise resistance to their passage would create impossible friction. Aristotle taught that a void is impossible. If stars are created, they are subject to physical laws of motion. Aristotle taught that divine spirits move the stars.

Simplicius countered Philoponus with a number of arguments. How could star stuff be like earth stuff? Would not the duration of a fall tend toward zero as the density of a medium decreases? If space were a vacuum, Simplicius contended, objects such as stars would have infinite speed.

Philoponus’ replies anticipated the great Renaissance scientists Galileo (1564-1642) and Simon Stevin (1548-1620). He correctly argued that the velocity of a body’s fall is not proportional to its weight. A millennium before Galileo, he proposed dropping two bodies of unlike weight from a tower and postulated that the time of the fall would differ little between the two objects.

He also speculated that any object dropped in a vacuum would require finite time to fall. And, contrary to Aristotle, he asserted that a vacuum is possible and saw no absurdity in supposing that motion can occur in such a void.

Having declared the stars to be of the same material as earth, Philoponus was forced to explain their movement. Aristotle attributed celestial movements to spirits. But his seventh-century critic suggested that the Creator had impressed movement upon the original universe. Inertial motion is a kind of “rest”, Philoponus argued. That is, once motion was imparted, an object in a void kept going because of inertia, without a further push. This impetus theory was revived in the thirteenth century by Peter John Olivi (c. 1248-1298) and has been incorporated into modern physics as momentum or kinetic energy theory.

This conception cut straight to the heart of another Aristotelian error. Aristotle had taught that air closing in behind a moving projectile propelled it. Philoponus disagreed, teaching instead that a medium such as air that resists the motion of a projectile cannot also propel that projectile. A stone moves because force is impressed onto it. Eventually it ceases to move because of counteracting resistance. If we throw a stone, it flies a distance. If we hang a stone from a light string and then stir the air with any device we choose, the stone barely moves. The cause of movement, once a stone leaves the throwing hand, resides in the stone itself.

A widespread religion of Philoponus’s time was pantheism, a belief system that sees God as equivalent to nature. In his rejection of this, Philoponus argued that the Creator transcends nature rather than being within it. He taught that God created matter ex nihilo (out of nothing) and endowed it with fundamental physical properties, possessing the capacity to develop according to natural laws from chaos to its present state. Having been created, nature exists without constant intervention by God. This radical conception shocked the pagans who believed the gods were imbedded within the material universe.

If Simplicius had difficulty with Philoponus’s refutations of Aristotle, he certainly did not know how to take his opponent’s even bolder assertion that this world is to be recreated by God.

Philoponus’s brilliance also burned brightly in his astronomical theories. Since, in his cosmology, the heavenly bodies are made of the same stuff as the earth, it follows that sun and stars are fiery. His everyday experience with burning substances told him that the color of anything, and therefore of a star, depends on the nature of its fuel. Differences in stellar magnitude and brightness are a function of different fuels.

He also claimed that celestial bodies are just as subject to change and decay as earthly bodies. Such changes are not observed in the stars because of their large masses, he reasoned, noting that even on earth we observe that the greater the mass of a body, the slower its decay.

Today we know that his guesses were shrewd beyond his time. While the color of a star is largely a function of its mass which determines its temperature, stars do produce characteristic spectra according to the elements of their composition. Remarkably, Philoponus arrived at his conclusions unaided by even the most primitive telescope.

The astute Alexandrian also tackled Aristotle’s ideas about the origins of the Milky Way. Aristotle had attributed the Milky Way and comets to gaseous exhalations rising from the earth. How can this be? asked Philoponus. Unlike comets, the Milky Way never changes in position or size. It doesn’t dim the moon. It is not subject to changes like the weather. The number of distinguishable stars behind it doesn’t affect its brightness. Yet he failed to recognize it as a blurred host of stars, placing it instead in the realm of things knowable only to God.

Philoponus rejected still other Aristotelian errors. In Aristotle’s thought, things move toward their affines, that is, toward objects possessing similar properties. Phrased more practically, this means air tends to rise. Earth will fall to rest with earth. Celestial objects are in an etheric class all their own. Nonsense, said John. Lift a shovelful of dirt and air rushes into the hole.

Philoponus taught that light is a directional phenomenon. Rays are not projected from our eyes to the object, but they move from the object to our eyes. This now seems obvious, but to early thinkers, attempting to explain the conic spread of light, it did not.

While almost all early religions and philosophers believed in either an eternal universe or one that emerged from an earlier substance (the body of a murdered god, for example) Philoponus argued strongly against the notions of infinite space and time. Since the world is a creation, it cannot be infinite, he hypothesized. His reasoning made use of infinite cardinal numbers and pointed out the logical problems found in infinite series. For example, if the amount of all numbers is infinite, and if the amount of all even numbers is infinite, there must be a one to one correspondence between all numbers and the even numbers. Commonsense says there should be twice as many odd and even numbers as there are even numbers. Since it seemed absurd to suppose there really are, infinities of any countable sort of thing are an absurdity, said Philoponus. He is the first person known to have made this argument.

His use of infinities anticipated modern concepts by thirteen hundred years. Current theory now takes us where Philoponus thought we could not go. But today’s cosmology also has mathematical and material proof that time and the universe are finite. Again and again Philoponus’s theology led him to insights surprisingly close to modern science. All these ideas were the outcome of working out the logical implications of creation and time.

John Philoponus is believed to have lived an extraordinary long and productive life. His reputation for hard work earned him the name, “Lover of Labor.” He was also a lover of books. According to legend, he was still alive when the Islamic armies under Amrou sacked Alexandria (c. 642-646). Muslims were not generally offended by Philoponus’s Christian writings because of his monophysite leanings. He supposedly discoursed on theology with the learned Amrou and pled that the Library of Alexandria be spared the torch. But acting on orders from home, Amrou burned the library anyway. Whether the legend is rooted in fact is unclear, but we do know that his own writings were taken by the Arab conquerors and lost to the West. Still, Islamic science seems to have been positively influenced through them.

Philoponus successfully challenged Simplicius and the fundamental errors of Aristotelian theory. His originality and keen insight helped pave the way for many of the discoveries of modern science. Reading him centuries later, Galileo praised Philoponus. But the Alexandrian’s greatest contribution is his demonstration that acceptance of the fundamental assertions of Scripture, especially the fact of creation, will direct us toward the truth. It is the clearest path to scientific enlightenment.


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Sorabji, Richard. Philoponus and the Rejection of Aristotelian Science. Ithaca, NY: Cornell, 1987.

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