Intro to Philosophy

Lesson 6:Descartes, the Rationalists, and Certainty

Rene Descartes

1596 – 1650 CE

La Haye (now Descartes), France

Lived mostly in Holland, died in Sweden.

“The Father of Modern Philosophy”

“If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.”

Mathematical contributions: Analytical geometry (x and y

axes) Predecessor of modern calculus

The Father of Modern Philosophy

Perhaps the biggest distinction between “modern” and “ancient” philosophy is the emphasis on method.

The “Flight from Authority”

Descartes changes the questions of philosophy to questions of method instead of substance.

Historically: The “Renaissance” and “Scientific Revolution” were

changing the perspective on common knowledge. The socio-political structures of Europe were in a time of

turmoil and upheaval out of traditional feudalistic states.

De omnibus dubitandum est

Descartes turned doubt into a useful tool into a full-blown method of acquiring truth.

“…to withhold my assent from matters which are not entirely certain or indubitable.”

By assuming that everything that can be doubted should Descartes hopes to find something which cannot be doubted and then build a philosophical understanding of the universe from the implications and consequences of that foundation.

The Method

If anything can be doubted—if there is one reason why something could not be true—then he will discard the whole idea.

The investigation is aimed at the founding principles of any idea instead of the surface level features or explanatory power it provides.

Sense Perception

Sense perception is problematic because: Sometimes the things we see are not in accord with

actuality (mirages, distance, etc.). Dreams complicate it further because we have

sensory experience in dreams which are, of course, also unreal.

Perceptions, however, must have a source, otherwise we would not be perceiving them, so they are not utterly dismissible, but they are also not something that can be accepted on its own premises.

The Evil Demon

Mathematics and geometrical concepts can form the basis of perception.

But it is possible that a powerful demon has so arranged the perceptible universe for humans that these cases appear real, but in fact, are not.

Thus mathematics is also not the best foundation because it can be doubted.

Existence

Existence might provide a touchstone for truth

Existence defined in terms of physical presence (space and matter) is doubtable in the same way that our perceptions are doubtable.

The alternative is that existence is a mental or non-physical construct.

Cogito, ergo sum

In terms of the mind, Descartes is aware that he doubts, and that doubting is a kind of thinking.

The function of thinking implies a thinker.

“I think, therefore I am.”

Existence as non-physical, or mental, is the cornerstone of all future philosophical reflection.

The Soul

The ‘I’ that thinks is non-physical.

Therefore, the source of thought is non-physical

The soul is therefore the thinking thing that exists.

The Exterior World

What we grasp of the exterior world is grasped by the mental connections implied between perceiver and perceived.

We know something because we mentally grasp its essence and build up from it imaginatively and through sense perception the mental image of it.

God

Our thoughts guarantee certain truths, but what guarantees the truth of our thoughts? (Remember the “evil demon”)

All effects have a cause

Thoughts are also effects that have been caused by something.

The thought of something must be caused by something which as at least as much reality as the thought itself.

I have an idea of God

Only a perfect being is sufficient to cause my idea of God

Therefore, God exists.

God, Pt. 2

The idea of a deceitful demon still persists.

God is a perfect being.

A perfect being would not deceive us.

Therefore, we can trust our thoughts as true.

What About Unicorns?

The ability to imagine something, like God or unicorns, does not mean they exist.

God is a perfect being.

A perfect being that does not exist is not a perfect being; or a perfect being exists by definition.

Therefore the ability to think about a perfect being implies that God exist.

External World

We possess the innate idea that we are both an immaterial thinking, and physical unthinking, thing (soul & body). This also applies to bodies as a concept (e.g., things that take up space).

These innate ideas are confirmed by sense experience in which I do not decide to perceive an external world, but rather it imposes itself upon me despite my will.

Thus the external world exists, but not perhaps as we perceive it.

Mind/Body

Dualism: the notion that the mind and the body are distinct entities.

Interactionism: the idea that soul and body comprise a whole (and are therefore not fully independent).

The mind and the body are connected through the brain as the primary communicative tool.

Criticisms

The idea of a presupposition-less philosophy is impossible. Eventually we all rely on basic assumptions that are not self-evident.

For instance, Descartes’ starting point was the observation that he is thinking, which implies he exists.

But nothing, so far, has proved this to be indubitable until he gets to his proofs for God as a guarantor of thought.

Criticisms

Sometimes Descartes can be logically inconsistent.

The idea that the soul is located in the pineal gland contradicts the idea that the soul is immaterial.

The fact that Descartes chose doubt as a method is doubtable… he did not doubt the idea that doubt is the best method (Kierkegaard).

Criticisms

Descartes is the historical turning point at which access to truth becomes a purely intellectual exercise with no conditions upon the thinker himself (Michel Foucault)

Mathematics and scientific data are objectively true in the sense that we can believe them regardless of our maturity as persons.

Mathematical truth, however, is not the fullest definition of truth, and Descartes is problematic because he reduced the acquisition of truth in its fullest sense to the intellectual assent to propositions.

Philosophy ever since has in some ways been a search for how to recover the subjective experience of truth.