1. A Brief Intro to Philosophy
What’s real, and how do you know it?

2. Finding the Bottom-most turtle…
After a lecture on cosmology and the structure of the solar system, William James was accosted by a little old lady. "Your theory that the sun is the centre of the solar system, and the earth is a ball which rotates around it has a very convincing ring to it, Mr. James, but it's wrong. I've got a better theory," said the little old lady. "And what is that, madam?" Inquired James politely. "That we live on a crust of earth which is on the back of a giant turtle," Not wishing to demolish this absurd little theory by bringing to bear the masses of scientific evidence he had at his command, James decided to gently dissuade his opponent by making her see some of the inadequacies of her position. "If your theory is correct, madam," he asked, "what does this turtle stand on?" "You're a very clever man, Mr. James, and that's a very good question," replied the little old lady, "but I have an answer to it. And it is this: The first turtle stands on the back of a second, far larger, turtle, who stands directly under him." "But what does this second turtle stand on?" persisted James patiently. To this the little old lady crowed triumphantly. "It's no use, Mr. James – it's turtles all the way down.“
— J. R. Ross, Constraints on Variables in Syntax 1967

3. Important Terms
Epistemology- the branch of philosophy that deals with knowledge, exploring what it means to “know” something
Metaphysics-the branch of philosophy that explores the fundamental nature of reality
Empiricism- The belief that knowledge of reality is best gained through the physical senses
Rationalism- The belief that knowledge of reality is best gained through logical reasoning, based on rational or self-evident principles

4. The debate goes back to ancient Greece…
Aristotle the Empiricist
Plato the Rationalist
“Reality” exists in the world of forms
People are born with innate ideas about reality
The physical world is only a copy of those ideal forms
Knowledge comes through logic and reason
“Reality” exists in the natural world, outside the human mind
Our ideas come from repeated observations of natural phenomena
Knowledge comes through observation and sensory input

5. Fast Forward to the Enlightenment…
Both empiricism and rationalism shaped metaphysics-- western civilization’s quest to understand “reality”—up to and including the scientific revolution
By the 1600s, people started to apply these tools to epistemology.
Many thinkers during this period were more concerned with how we KNOW something is real than they were with knowing what IS fundamentally real, starting with…

6. Rene Descartes! French philosopher (1596-1650)
Felt senses could easily be deceived (e.g., in dreams or hallucinations)
Believed the only path to sure knowledge was to begin by doubting everything
His most famous epistemological argument: Cogito Ergo Sum
Or, “I think, therefore I am”
What does this argument imply about knowledge?
What does it imply about the human mind?

7. Rationalism and Science
Most European philosophers subscribed to Descartes’ rationalist theory, of knowledge.
In many ways, rationalism shaped the course of the scientific revolution
Laws of physics and mathematical principals seen as reliable paths to knowledge
Assumption that the natural world must be shaped and governed by principles of physics and math
The Scientific Method becomes the accepted path to true knowledge

8. The Philosophical Brexit
Most scientists and philosophers, while rationalists, were still influenced by empiricism.
A group of British philosophers took empiricism to a new extreme
They British Empiricists, like Aristotle, argued that before we can deal with ideas we need to have sensory experience
Knowledge comes from our senses (from the outside in), rather than our minds (from the inside out)
One of the most notable empiricists was…

9. John Locke! British Philosopher (1632-1704) Locke’s epistemology:
Human Mind is a blank slate (tabula rasa)
Sensory experiences create impressions which lead to ideas
The idea is the fundamental unit of the mind
We learn and develop more complex ideas, beliefs, and attitudes as we group ideas together (associationism)
Ultimately, the five senses give us access to true knowledge

10. Could there be any other types of knowledge?
The debate goes on…
Empiricism
Rationalism
Pros
Cons
What is the inherent problem in framing the debate about knowledge this way?
Could there be any other types of knowledge?