A scientist centuries ahead of his time

Faith and science Peter Hodgson
TN THE EARLY centuries the works of Aristotle were widely known, and
he was considered to have said the last word on a wide range of subjects. Up to and including the Middle Ages, philosophers usually taught by expounding the works of Aristotle, sometimes elaborating them in matters of detail.
Very few of them radically challenged Aristotle, and one of these was John Philoponus, a Neoplatonist who lived in Alexandria in the 6th century. He was born a pagan and later became a Christian, and it was his Christian beliefs that led him to make his incisive criticisms of the pagan cosmology of Aristotle.
Many of his ideas were far in advance of his time, and he anticipated some of the work of Buridan on the dynamics of motion. Aristotle had many different explanations for different problems, and Philoponus unified them by reference to the creative power of God. Although he challenged many of Aristotle's beliefs, he retained the conceptual framework, and to the end of his life referred to him as the prince of physicists.
The basic problem in dynamics is the motion of projectiles: why does a javelin continue to move forward after it has left the hand of the thrower?
Aristotle suggested that the thrower influences the surrounding air so that it carries the javelin forward. This may easily be shown to be implausible, and so Philoponus suggested that a kinetic force is impressed on the body by the thrower, and that this continues to move it forward until dissipated by fractional forces. This is very similar to the later work of John Buridan in Paris in the 14th century.
Philoponus' impetus theory was known to the Islamic philosophers of the 12th century such as Avicna, but Maier and Sorabji consider that it is unlikely to have been transmitted to the Latin West early enough to influence Buridan. Impetus theory was developed independently in the Middle Ages, generated by the same Christian doctrine of creation.
Aristotle's ideas on motion persisted until the high Middle Ages, and were held by Albertus Magnus and by Thomas Aquinas. Buridan went beyond Philoponus by invoking the creative power of God, who put everything in motion and gave it the impetus to continue.
For Buridan, impetus was a permanent quantity, so that if there were no contrary forces or resistance the motion would continue forever. He furthermore considered that impetus varies as the velocity of the projectile and its quantity of matter; although not expressed mathematically this is equivalent to the definition of momentum as the product of velocity and mass. Thus the main credit for the development of impetus theory belongs to Buridan.
Philoponus also said, contrary to Aristotle, that all bodies would move in a vacuum with the same speed whatever their weight and that bodies of different weight falling from the same height would reach the ground at about the same time, a statement usually associated with Galileo.
Philoponus is an example of a man who did brilliant work before the social conditions were ripe for its general acceptance. Had they been favourable, modern science might have developed much earlier than it did. He wrote in Greek, and few of his writings were translated into Latin in time to influence the philosophers of the high Middle Ages.
He was a monophysite, believing that Christ has only one nature, a doctrine that was condemned by the Council of Chalcedon in 451. Philoponus was also the first to say that Genesis was written for spiritual and not for scientific instruction, a wise statement that was too far in advance to be congenial to contemporary theologians.