Early Modern Philosophy 1: Background.
Dates for our philosophers: Broadly, these figures
cover the 17th & early 18th centuries.
Descartes: 1596- 1650
Hobbes: 1588-1679
Pascal: 1623-1662
Spinoza: 1632-1677
Leibniz: 1646-1716
Locke: 1632-1704
Berkeley: 1685-1753
Context: The scientific revolution.
Nicholas Copernicus: 1473-1543:
Placed the sun at the centre of the solar system;
Argued only that his system was as good, on the
evidence, as the Ptolemaic (earth-centered) system.
Galileo: 1564-1642
* Developed the first astronomically useful telescope.
* Formulated a law for the motion of falling bodies:
Constant acceleration & Parabolic paths.
* Noticed the periodicity of the pendulum.
* Observed the moons of Jupiter.
* Defended an early version of the principle of inertia.
* Argued that Copernicus’ system of astronomy was
literally correct, not merely another way to ‘save the
phenomena’ (& was imprisoned by the inquisition).
* Thought that a fully mathematical account of the
working of the world could, in principle, be perfected.
Tycho Brahe: 1546-1601
* Built massive (naked eye) instruments
* Using them, he made much more precise
measurements of the paths of the planets across the sky.
* Developed his own system of astronomy, earthcentered for the moon, Mercury & Venus, but with the
other planets orbiting the sun.
Johannes Kepler: 1571-1630
 Worked for Brahe.
 Developed a model of the orbit of Mars that fit
Brahe’s data: An ellipse with the sun at one focus.
 Three laws of planetary motion:
1. Planets move in ellipses with the sun at one focus.
2. The area of the ellipse ‘swept out’ by a line joining the
planet to the sun is constant (so the planet moves
quicker as it gets closer to the sun, and slower when
it’s further away).
3. The square of the period of a planet’s orbit changes as
the cube of the mean orbital radius (that is, the
planet’s average distance from the sun):
T2=k R3
where k is Kepler’s constant.
Isaac Newton: 1642-1727.
 Invented the calculus (Leibniz invented it
independently).
 Applied it to develop his laws of motion and theory of
gravity, which explains Kepler’s laws.
 His great work of physics, Philosophia Naturalis
Principia Mathematica (The Mathematical Principles
of Natural Philosophy) appeared in 1687.
Philosophical Challenges:
1. Turning away from Aristotle on perception &
metaphysics: Since the 13th century, philosophy in
Europe had focused on Aristotle (whose works came to
Europe through Arab sources). Ideas about perception,
and metaphysics in general, were shaped by Aristotelian
positions, modified (in some cases) to reconcile them
with Catholic doctrines.
The scientific revolution tossed out many of Aristotle’s
views on nature and human knowledge:
a. Inertia: Aristotle thought that a force was required to
keep things moving, and that if the force was
withdrawn, the object would come to a stop. But this
doesn’t really work well for ballistic motions (which
were a serious practical concern in gunnery).
b. Earth-centered astronomy: For Aristotle, heavy things
fall because the centre of the Earth is the centre of the
universe, and it’s where such things belong. This
never worked terribly well—while it’s easy to treat the
fixed stars as turning on a sphere with the earth at its
centre, the sun and other ‘planets’ (= wanderers) were
tricky to fit in and the devices uses (epicycles) didn’t
fit well with Aristotle’s physics, which demanded
‘perfect’ circular motion centered on the Earth for
everything above Earth’s atmosphere.
c. Perception: For Aristotle, things really were as they
appear to us to be, at least when our eyes were
working properly. Objects have sensible characters
(colours, scents, etc.), or ‘species’, which they send
out. For instance, light activates the transparency of
the air, which allows visible species to be transmitted
to our eyes, where they produce an awareness in us of
the property of the object.
1. Mathematicized physics:
a. Focuses on measurable quantities: Time, space and
Euclidean geometry (which had been an ideal model
for human knowledge since the ancient Greeks: On
the entrance of Plato’s Academy was the slogan, “Let
no man enter here unless he knows geometry”.
Regards such mathematicized properties as completely
describing the causal workings of the world.
b. Creates problems for properties that we experience
through our senses: How can colour, smell, taste, etc.
fit with this mathematical account? It seems they
aren’t really out there at all: The causal processes
that link the object to our senses operate by means of
the mathematical/geometrical properties that physics
deals with, not by transmitting anything like ‘colour’
from the object into our minds.
c. Philosophers had to try to build a new account of
perception and human knowledge, more generally,
that would fit with the new science. It had to allow
that the physical world works as the physicists say it
does, and it had to show (more subtly) that we humans
could figure this physics out and get it right using the
methods of science. Lastly, it had to apply these ideas
of physics to human beings as well—which leaves a
real problem for us: If colours are all in our heads, but
our heads (and brains) are just physical objects too, it
seems there’s no place left for the colours to be. But
we see them, we are conscious of them, and when we
think in those terms (of how we describe our
experiences) it seems talk of colours is indispensable.
This is one of the roots of (bad old) DUALISM.
d. The philosophical response to this challenge is still
underway; a lot of progress has been made, but the
problem of consciousness is just one example of a
fashionable contemporary issue whose roots (as I see
them) lie precisely in this problem.