Quiz: Locke vs. Berkeley

If a tree falls in a forest and no one is present to hear it, does it make a sound?

This famous riddle has appeared in many forms since George Berkeley first wrote about the non-existence of imagined trees in a park (A Treatise Concerning the Principles of Human Knowledge, 1710). And it has been answered in different ways since that time, critically depending on the definition of "sound" and "hearing."

Each of the five questions below are answers to the same questions and trees falling, hearing and sound. Answer each question according to the conditions prescribed.

Recall that Primary Qualities include size, shape, position, and local motion and divisibility. Secondary qualities include color, sound, odor, flavor, hot and cold.

QUESTION 1: Aristotle

Aristotle (4th century BC) put more faith in his senses than did his professor Plato. Plato dramatized the separation between the world and the senses in the parable of the cave. We are all like prisoners chained to stones seeing the shadows of the world projected on the back wall of the cave. We cannot perceive the world directly, only through the representations produced by our senses. Would Arisotle's tree make a sound?

Aristotle remarks that "sound is a certain motion of air" and that the air inside the ears is immovable "in order for it accurately to sense all the varieties of motion."

QUESTION 2: John Locke

Locke made a distinction between Primary qualities and Secondary qualities. Primary qualities exist in the world, but the Secondary qualities are produced in the mind. Does Locke's tree make a sound?

QUESTION 3: George Berkeley

George Berkeley believed that all qualities -- both Primary and Secondary -- are produced in the mind. In fact, trees do not exist at all without a mind to perceive them. Does Berkeley's tree make a sound?

QUESTION 4: Scientific American Magazine

This famous magazine took up the question in 1884. It reflects the scientific/empirical thinking of the late 19th century. Did their tree make a sound?

QUESTION 5: Nils Bohr

Albert Einstein asked Bohr, the father of Quantum Mechanics, if he "really believed that 'the moon does not exist if nobody is looking at it.'" Recall that Einstein criticized Quantum Mechanics by saying that 'God doesn't play dice with the world.' Would Bohr's tree make a sound?