1. 1
Introduction

2. Introduction
“ What is real? How do you define real? If you’re talking about what you can feel, what you can smell, what you can taste and see, then real is simply electrical signals interpreted by your brain. This is the world that you know.”—Morpheus’s answer to Neo in The Matrix, 1999

3. Early Philosophy of Perception
Plato and “The Allegory of the Cave”

4. Early Philosophy of Perception
Perception and your sense of reality are the products of evolution:
Sensory systems provide a survival advantage
Importance of type of energy in the environment for an animal determines which senses have developed
Human senses are limited to only certain kinds of energy in the environment
Therefore, humans’ sense of reality is also limited

5. Early Philosophy of Perception
Some species sense energies that humans cannot:
Bees see ultraviolet light
Rattlesnakes sense infrared energy (e.g., heat)
Dogs and cats can hear sounds of higher frequencies
Birds, turtles, and amphibians use magnetic fields to navigate
Elephants can hear very low-frequency sounds, which are used in communication

6. Figure 1.5 Honeybees (a), snakes (b), dogs (c), and birds (d) are able to sense a variety of stimuli that humans cannot
wolfe2e-fig jpg

7. Early Philosophy of Perception
Change is essential for perception
“You can never step into the same river twice.”—Heraclitus (540–480 BCE)
Our perceptual systems respond to novelty and change
Adaptation: A reduction in response caused by prior or continuing stimulation
If there is no change in stimulation, our senses adapt and we no longer notice the stimulation

8. Early Philosophy of Perception
Perception starts with energy from the environment
Democritus (460–370 BCE): The world is made up of atoms that collide with one another, and sensations are caused by atoms that make contact with our sense organs
Sensation is the result of the physical interaction between the world and our bodies
Perception is the processing and interpretation of sensations
Sensory transducer: A receptor that converts physical energy from the environment into neural energy

9. Nativism and Empiricism
Nativism: The idea that the mind produces ideas that are not derived from external sources, and that we have abilities that are innate and not learned
Dualism: The idea that both mind and body exist and are separate entities
Both of these ideas were championed by Descartes

10. Nativism and Empiricism
René Descartes (1596–1650) argued for mind-body dualism, the idea that the universe consists of spirit/soul and matter/body
“I think, therefore I am.”

11. Nativism and Empiricism
Monism: The idea that mind and matter are formed from, or reducible to, a single ultimate substance or principle of being
Materialism: A particular form of monism. The idea that physical matter is the only reality and everything, including the mind, can be explained in terms of matter and physical phenomena
Mentalism: Another form of monism. The idea that the mind is the true reality and objects exist only as aspects of the mind’s awareness

12. Nativism and Empiricism
Empiricism: The idea that all knowledge comes through the senses
Opposed to nativism, which says that some knowledge is innate
According to empiricism, perception is the source of all knowledge about the world

13. Nativism and Empiricism
Thomas Hobbes (1588–1678) believed that everything that could ever be known or imagined had to be learned through the senses

14. Nativism and Empiricism
John Locke (1632–1704) sought to explain how all thoughts, even complex ones, could be constructed from experience with a collection of sensations
We are born with a tabula rasa (blank slate) for a mind on which experience writes

15. Nativism and Empiricism
George Berkeley (1685–1753) studied ways in which perception is limited to the information available to us through our eyes
Concluded that all of our knowledge about the world must come from experience, no matter how limited perception may be
“To be is to be perceived.”

16. Figure 1.9 Berkeley’s exploration of how vision works
wolfe2e-fig jpg