cm [003] philoponus' impetus

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PHILOPONUS’ IMPETUESPM [003] In search for the cause of motion


John Philoponus

The Aristotelian theory of forced motion encountered criticism in the Medieval age, first and formally by John Philoponus in the 6th century.Philoponus (AD 490-570) in Greek means "lover of work“. He was so called because he spent most of his time studying. He was an Alexandrian Christian who disagreed with Aristotle's philosophy. One of his most important achievements in spear heading Alexandria’s science was his theory of impetus.


Philoponus’ major argument against Aristotle was on the cause of motion. He opposed to the idea of a medium of force such as air because it would resist the motion of a projectile and definitely could not also propel that projectile.

The Medium of Force

Projection motion

Air resistance


Motive Cause - Impetus

Philoponus believed that a stone moved because something like a force had impressed onto it. The stone absorbed the force, moved a little faster and continued to move on. It eventually had to cease motion because of encountering situations such as resistance from the air or collision with another body. The cause of movement or the motive force, Philoponus concluded, resided within the stone itself. He called this something ‘impetus’.

BEFORE

AFTER Impetus


Eternal Celestial Motions

As for the celestial movements Aristotle attributed them to the power of spirits. But Philoponus suggested that the Creator had impressed movement upon the original universe in the first place and the universe went on with the momentum impressed on it. In the same manner as the stone projectile, once the cause of motion was imparted, an object in a void would keep on going because of impetus, without any further push.


Breaking the Earth-Heaven Barrier

This endowment by God did not decay with time. So it was no longer necessary to postulate a variety of angelic movers working on the heavenly bodies.

This is in the truth of the law of conservation of impetus though Philoponus did not explicitly recognized it.

This conception, besides establishing impetus as a individually existing entity, it was also a major step in breaking down the difference between the movement of heavenly and earthly objects as conceived by Aristotle.


Philoponus vs Aristotle

To Aristotle, motion is an effect caused by an external agent – an external force. In Philoponus’ theory, motion is an intrinsic property of the moving object itself. Impetus, the driving agent, is first imparted to an object and set the object in motion and later abides within the moving object on its journey.

This is for the first time in a thousand years when the ideas of Aristotle were seriously and challenged and gain acceptance.


What is the Nature of Impetus?

Impetus seems to be something that exists naturally in this world. It appears to Philoponus that it is a fundamental fact of nature and did not give further elaboration on it.

?


The Impetus Piece

Understood or not, we have been able to obtain another important piece for our cause of motion puzzle after velocity –impetus.

Velocity

Impetus


BURIDAN’S IMPETUSTo be continued on CM [004]

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cm [003] philoponus' impetus

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