Beginning the Enlightenment, Chapter 9

Descartes, Plato

What are the three conditions for having propositional knowledge?

• You must believe in the idea

• The idea must be true

• You must have good justifications for you belief in the idea

What is skepticism?

The view that we lack knowledge in some fundamental way and that many (or all) of our beliefs are false or unfounded

What are the two ways of acquiring knowledge?

• Reason, a priori → independent of or prior to sense experience

• Sense experience, a posteriori → depends fully on sensation

Who are the most notable rationalists and empiricists?

• Rationalists: Plato and Descartes

• Empiricists: Locke, Berkeley, and Hume

How did Plato view the source of knowledge?

He said the source of knowledge is reason, and we can be sure of our ability to acquire knowledge since we can identity false beliefs and grasp mathematics and logical truths through reason

How does Plato conceive of reality?

Reality is made up of two worlds, the physical and the eternal → physical is fleeting and accessed through sense experience; eternal is non-physical, changeless, and accessed only through reason

What are the Forms?

They are the perfect conceptual models for every existing thing, residing only in the eternal world → proposed by Plato

What are Plato’s views on innate knowledge?

Plato supports the idea of innate knowledge, positing that knowledge of the Forms is already present at birth, inscribed in our minds from a pervious existence

How does Descartes initially embrace skepticism?

He says that all beliefs based on sense experience are unreliable, citing his dream and evil genius scenarios:

• Dream → we have no certain indications by which we can distinguish between dreaming and wakefulness

• Evil genius → there could be an evil God systematically deceiving one, manipulating every though and aspect of reality

How does Descartes discard his skepticism?

He realises he cannot doubt that he exists, since if he has thoughts and doubts, he must exist → first principle: ‘je pense, donc je suis’ / ‘cogito, ergo sum’

How does Descartes expand upon his first principle?

He argues that if he perceives something clearly and distinctly, he must know it with certainty since a perfect God would not allow him to be deceived

How does Descartes argue for rationalism?

Using the wax thought experiment:

• When watching candle wax melt, our senses tell us that melted wax is a new, different object than solid wax, but the mind knows better

• Rationalism informs us that melted wax is still wax

• Relying only on sense experience would lead us to believe that the wax had disappeared, being replaced by a new liquid substance

• In this scenario, sense experience leads to an incorrect belief, while rationalism supports a correct one