French philosopher, mathematician and physical scientist (optics, physics, physiology)

Father of Early Modern Rationalist Philosophy Early Modern Philosophy is characterized by

the thesis that genuine knowledge can be achieved by humans through the use of their rational and perceptual faculties independent of any form of divine revelation. Hence, early modern philosophy arises

coincident with the emergence of natural science as we know it today.

1

Rationalism asserts that some fundamental knowledge is a priori (Latin: “from the former/prior”), i.e. knowledge independent of sensation and perception Typically, rationalism maintains that

knowledge of universal and necessary truths is a priori

Empiricism, in opposition to Rationalism, asserts that all knowledge is a posteriori (Latin: “from the latter), ie. Knowledge dependent upon sensation or perception.

2

Copernicus (Polish; 1473-1543) Astronomy: Heliocentric solar system Challenge to Church-endorsed Geocentric universe

Francis Bacon (English; 1561-1626) Development of the scientific method

Galileo (Italian; 1564-1642) Mathematician, Physicist & Astronomer; Copernican Challenge to Church’s claims of divine revelation of

natural laws Kepler (German; 1571-1630)

Discovered laws of planetary motion Boyle (Irish; 1627-1691)

Developed experimental chemistry; worked in mechanics, medicine, hydrodynamics

Newton (English; 1642-1727) Fundamental laws of physics; classical mechanics Develops the calculus (independently, so too does

Leibniz (1646–1716))3

Is the mind different from matter?

Should we adopt the scientific method to advance knowledge?

What can we know with certainty?

4

Substance = substrate securing identity of an individual objectConsider pin cushion model

Object = substance (cushion) + attributes (pins)

Cushion remains constant while pins are replaced: substance remains constant while attributes are replacedSome attributes are essential (irreplacable without destruction of the object)

Others are merely accidental5

Material Substance (Matter): Substrate in an object whose essence is To be extended in space Governed by the laws of the physical sciences Incapable of thinking/feeling

Mental Substance (Mind): Substance in an object whose essence is To think/feel To be unextended and not in space Not governed by the laws of the physical sciences

Dualism: A person = combination of two substances

Is it possible for these two substances to interact?6

ConceivabilityWe can each conceive of ourselves as existing without our bodies

Hence, it is possible for the mind to exist without a body

If it is possible that x exists without y existing, then x is different than y

Hence, the mind and body must be fundamentally different substances

7

Although may be possible to conceive of x and y as different, this does not imply that x and y must be different things, objects or substances

Eg: It is possible to conceive of Barak Obama as being different from the president. Nevertheless, they are the same.

Thus, even if it is possible to conceive of my mind as being different from my body, they may be the same

8

The mind is both intentional and conscious Intentional = represents both what is real

and fictious correctly and incorrectly Conscious = What it is like to think & feel

& perceive

Material Substances can’t be intentional or conscious

Hence a mental substance can’t be a material substance

9

Perhaps material substances are indeed intentional: Can machines think? Are computers intelligent? Are brains thinking things?

10

Foundationalism: By appropriate use of their rational and perceptual faculties, humans can autonomously come to know with appropriate certainty the fundamental truths of pertaining to both material and mental substances, i.e. discover the true principles of science. This is the basis of all other knowledge

Skepticism Denies Foundationalism Asserts that knowledge is impossible because

certainty is impossible

Meditation I: Descartes’ provisional argument on behalf of the skeptic Knowledge requires certainty. Certainly is either empirical or a priori Empirical certainty is impossible because of

Illusion: hence, no empirical certainty regarding attributes of material substances

Hallucination : hence, no certainty regarding the existence of any particular material substance

Dream Hypothesis: hence, no certainty regarding the existence of the material universe generally

A priori certainty because of Evil Demon hypothesis

Hence, certainty is impossible Hence, knowledge is impossible

Cogito, ergo sum! No evil demon could delude one about one’s own

existence Thus, some a priori knowledge is possible! Each person can be a priori certain and have

genuine a priori knowledge about His/her own individual existence as a mental

substance The existence and content of his/her own current

ideas (i.e. psychological or mental attributes). Thus, one can know with a priori certainty what one

believes about God The material universe.

Thus, one may know with certainty the content of one’s idea of God as the perfect being.

Thus, Anselm’s Ontological Argument is certain and sound.

Hence, God exists! God’s existence implies that the Demon

Hypothesis is false. Hence, a priori reasoning can provide

certainty. Hence a priori knowledge of all of logic and

mathematics is possible. However, does the example of evil

sophomores refute the Cogito?14