Great IdeasKnowing and thinking
The senses and experience
What we learn by seeing, hearing and touching, and what we can't.
The question
What can our senses teach us, and what can't they? Do we see the world as it really is?
How the books answer
Oldest first. Each stop is our own short summary of what the author argued; follow the link to the rung for the whole lesson.
c. 369–360 BC
Plato, Theaetetus, Sophist, Cratylus and Parmenides
The young mathematician Theaetetus suggests that knowledge is simply perception. Socrates tests the idea: the same wind feels cold to one person and warm to another, and we judge things the senses alone cannot, such as sameness and difference. So knowing must be more than sensing.
“I see, my dear Theaetetus, that Theodorus had a true insight into your nature when he said that you were a philosopher, for wonder is the feeling of a philosopher, and philosophy begins in wonder.”
c. 350–322 BC
Aristotle, On the Soul, and the short works on sense, memory, sleep and dreams
Aristotle explains that a sense takes in the form of a thing without its matter, as wax takes the shape of a signet ring without the metal. Each sense has its own objects, like color for sight and sound for hearing. He trusted the senses as our starting point for knowing nature.
1689
John Locke, An Essay Concerning Human Understanding
Locke traces all ideas to experience. He separates qualities like size and shape, which he thought are really in things, from qualities like color and taste, which arise in us. His question of how far our ideas copy the world set the agenda for the next century.
“Let us then suppose the mind to be, as we say, white paper, void of all characters, without any ideas; how comes it to be furnished?”
Go to the rung: Locke: An Essay Concerning Human Understanding
1704
Isaac Newton, Optics
Newton's prism experiments show that white sunlight is a mix of rays bent by different amounts. He adds a careful remark: the rays themselves are not colored. Color is the sensation they stir up in us.
“For the Rays to speak properly are not coloured.”
1710
George Berkeley, A Treatise Concerning the Principles of Human Knowledge
Berkeley argues that if color and taste exist only in the mind, so must shape and size, since we never meet one without the other. Things exist as perceived. He believed this answered doubt, since the world we see is the real world, kept in being by God.
“Their ESSE is PERCIPI, nor is it possible they should have any existence out of the minds or thinking things which perceive them.”
1748
David Hume, An Enquiry Concerning Human Understanding
Hume says that all our ideas are copies of impressions from the senses or feelings. When a word stands for no impression at all, we should be suspicious of it. Experience is our only guide to matters of fact, and it works by habit.
Go to the rung: Hume: An Enquiry Concerning Human Understanding
1781; second edition 1787
Immanuel Kant, The Critique of Pure Reason
Kant agrees that knowledge begins with experience but says the mind gives experience its shape. We see the world in space and time and as linked by causes because that is how our minds must take it in. What things are in themselves, apart from us, we cannot know.
“That all our knowledge begins with experience there can be no doubt. … But, though all our knowledge begins with experience, it by no means follows that all arises out of experience.”
1890
William James, The Principles of Psychology
William James studies experience as a scientist of the mind. He notices that we never get pure sensations; experience flows like a stream, and attention picks out what we notice. What we see depends partly on what we are ready to see.
“Consciousness, then, does not appear to itself chopped up in bits.”
For young readers
Your five senses are how you meet the world: seeing, hearing, touching, tasting and smelling. They teach you a lot! But they can be fooled. A straw in a glass of water looks bent, but it isn't.
Here's a puzzle the great thinkers loved: is a strawberry red when no one is looking? Newton said light rays aren't really colored; the color happens when light meets our eyes and brain. Try it: what color is your room in the dark?
Talk about it
- Can you think of a time your eyes or ears fooled you?
- Is the strawberry red when no one is looking? What would Newton say? What would Berkeley say?
- Put one hand in warm water and one in cold, then both in lukewarm water. What happens? What does that tell you about your senses?
- What do you notice when you pay close attention that you usually miss?
Where else on the site
- Words for the Five Senses
- Observing Like a Scientist
- Light and Color
- You Can't Remember What You Didn't Notice
- Nerves, Senses and the Brain
Every rung tagged with this idea:
These pages are our own short synthesis, written for families. They were inspired by Mortimer J. Adler's Syntopicon, the index of great ideas in volumes 1 and 2 of Great Books of the Western World, but the questions, summaries and groupings are ours, not the Syntopicon's. Short excerpts come from public-domain translations, credited where they appear.