1. The Pre-Copernican Period
Roger Bacon William of Ockham Jean Buridan
Nicolas of Oresme Nicholas of Cusa Nicholas Copernicus

2. Roger Bacon (1214-1294) observation/experimentation deduction
hypothesis
falsification
Early European advocate for the empirical study of the natural world (Aristotle, Alhazen)
Doctor Mirabilis
Opus Majus (reform of medieval university curriculum)
Calendrical reform
Optics

3. Development of Modern Scientific Method
Attempting to understand the structure and behavior of the cosmos
in the 16th and 17th centuries gave rise to modern science.
Roger Bacon ( )
Francis Bacon ( )
Galileo Galilei ( )
Robert Hooke ( )
Isaac Newton ( )

4. William of Ockham ( )
Commentaries on Peter Lombard’s Sentences
frowned upon by Church/Pope
Doctrine of Apostolic poverty
Only faith gives us access to theological truths
Science is a matter of discovery; God is the only
ontological necessity
Advocate of nominalism, father of modern
epistemology (no supra-individual ideals)
Occam’s Razor (ontological parsimony) – Entia non
sunt multiplicanda sine necessitate
Is Occam’s Razor an outdated remnant of 14th century theological-scientific intellectual conflict?

5. Jean Buridan (1295 – 1363)
Theory of impetus (precursor of inertia/momentum)
impetus = weight x velocity
“Should two courses be judged equal
then the will cannot break the deadlock,
all it can do is to suspend judgement
until the circumstances change,
and the right course of action is clear.”

6. Advances in understanding of motion - I
In Aristotelian physics and object continues (un-natural) motion only while
a continuous force acts – thus anti-peristasis was invoked.
John Philoponus (490 – 570) rejected Aristotle's dynamics and proposed
the concept of impetus: an object moves and continues to move
because of an energy imparted in it by the mover and ceases the movement when that energy is exhausted.
He introduced a new period of scientific thought based heavily on three premises: (1) The universe is a
product of one single God, (2) the heavens and the earth have the same physical properties, (3) and the
stars are not divine. With these principles Philoponus questioned Aristotle's' view of dynamics and cosmology.
He argued that motion can occur in a void and that the velocity of a falling object is not based on its weight.
He also held that God created all matter with its physical properties and with natural laws that would allow
matter to progress from a state of chaos to an organized state forming the present universe. What remains
of his writings indicate that he used the same didactic methods of reasoning that modern science uses and
that he performed genuine experiments.
Avicenna (980 – 1037) concluded that motion was a result of an inclination (tendency to motion) transferred to the
projectile by the thrower, and that projectile motion in a vacuum would not cease.  He viewed inclination as
a permanent force whose effect is dissipated by external forces such as air resistance.

7. Advances in understanding of motion - II
Jean Buridan named the motion-maintaining property impetus. Moreover, he rejected the view that the impetus dissipated spontaneously (this is the big difference between Buridan's theory of impetus and his predecessors), asserting that a body would be arrested by the forces of air resistance and gravity which might be opposing its impetus. Buridan further held that the impetus of a body increased with the speed with which it was set in motion, and with its quantity of matter. Clearly, Buridan's impetus is closely related to the modern concept of momentum. Buridan saw impetus as causing the motion of the object. Buridan anticipated Isaac Newton when he wrote:
...after leaving the arm of the thrower, the projectile would be moved by an impetus given to it by the thrower and would continue to be moved as long as the impetus remained stronger than the resistance, and would be of infinite duration were it not diminished and corrupted by a contrary force resisting it or by something inclining it to a contrary motion (Questions on Aristotle's Metaphysics XII.9)
While anticipatory of Newtonian physical theory, Buridan viewed his ideas as corrections to Aristotelian physical theory.
The theory of impetus was also adapted to explain celestial phenomena in terms of circular impetus.
"God, when He created the world, moved each of the celestial orbs as He pleased, and in moving them he impressed in them impetuses which moved them without his having to move them any more...And those impetuses which he impressed in the celestial bodies were not decreased or corrupted afterwards, because there was no inclination of the celestial bodies for other movements. Nor was there resistance which would be corruptive or repressive of that impetus."

8. Advances in understanding of motion - III
Tunnel thought experiment and pendula
 Giambattista Benedetti ( ) modified the growing theory of impetus to involve linear motion alone:
"…[Any] portion of corporeal matter which moves by itself when an impetus has been impressed on it by any external motive force has a natural tendency to move on a rectilinear, not a curved, path.”

9. Nicole Oresme (1320–1382)
Evidence for and against the daily rotation of the Earth on its axis.
If the Earth were moving and not the celestial spheres, all the
movements that we see in the heavens that are computed
by the astronomers would appear exactly the same as if the
spheres were rotating around the Earth.
Rejected the physical argument that if the Earth were moving the air
would be left behind causing a great wind from east to west.
In his view the Earth, Water, and Air would all share the same
motion.
Scriptural passage that speaks of the motion of the Sun, Oresme
concludes that "this passage conforms to the customary usage
of popular speech" and is not to be taken literally.
More economical for the small Earth to rotate on its axis than the immense sphere of the stars.
Oresme developed the notion of incommensurate fractions, fractions that could not be expressed as powers of one
another. From this, he argued that it was very probable that the length of the day and the year were
incommensurate (irrational), as indeed were the periods of the motions of the moon and the planets.
From this, he noted that planetary conjunctions and oppositions would never recur in quite exactly the
same way. Oresme maintained that this disproves the claims of astrologers who, thinking "they know with
punctual exactness the motions, aspects, conjunctions and oppositions… [judge] rashly and erroneously about
future events."

10. Nicholas of Cusa (1401-1464) Became acquainted with Georg Peuerbach
Advocated reform of Julian calendar and
computus of Easter
The earth is a star like other stars, is not the
center of the universe, is not at rest,
nor are its poles fixed. The celestial
bodies are not strictly spherical, nor
are their orbits circular. The difference
between theory and appearance is
explained by relative motion.
Of Learned Ignorance (1440)

11. Nicholas Copernicus (1473-1543)
Copernicus’ Influence
Commentariolus
On the Revolutions of the Heavenly Spheres