"If a tree falls in the forest, and no one is around to perceive it, does it make a sound?"
Philosopher George Berkeley, in his work, A Treatise Concerning the Principles of Human Knowledge (1710), proposes, "But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park [...] and nobody by to perceive them. [...] The objects of sense exist only when they are perceived; the trees therefore are in the garden [...] no longer than while there is somebody by to perceive them." Nevertheless, Berkeley never actually wrote about the question.
Berkeley's example is referred to by William Fossett twenty years later in a consideration of the emergence of meaning: "[T]ease apart the threads [of the natural world] and the pattern vanishes. The design is in how the cloth-maker arranges the threads: this way and that, as fashion dictates. [...] To say something is meaningful is to say that that is how we arrange it so; how we comprehend it to be, and what is comprehended by you or I may not be by a cat, for example. If a tree falls in a park and there is no-one to hand, it is silent and invisible and nameless. And if we were to vanish, there would be no tree at all; any meaning would vanish along with us. Other than what the cats make of it all, of course."
Some years later, a similar question is posed. It is unknown whether the source of this question is Berkeley or not. In June 1883 in the magazine The Chautauquan, the question was put, "If a tree were to fall on an island where there were no human beings would there be any sound?" They then went on to answer the query with, "No. Sound is the sensation excited in the ear when the air or other medium is set in motion." This seems to imply that the question is posed not from a philosophical viewpoint, but from a purely scientific one. The magazine Scientific American corroborated the technical aspect of this question, while leaving out the philosophic side, a year later when they asked the question slightly reworded, "If a tree were to fall on an uninhabited island, would there be any sound?" And gave a more technical answer, "Sound is vibration, transmitted to our senses through the mechanism of the ear, and recognized as sound only at our nerve centers. The falling of the tree or any other disturbance will produce vibration of the air. If there be no ears to hear, there will be no sound."
There is a well-known story of Hui-neng, a well-respected Buddhist monk who later became known as the founder of the Zen school, who one day happened to be passing by two monks.
"Two monks were arguing about the temple flag waving in the wind. One said, "The flag moves." The other said, "The wind moves." They argued back and forth but could not agree.
The Sixth Ancestor said, "Gentlemen! It is not the wind that moves; it is not the flag that moves; it is your mind that moves." The two monks were struck with awe."
- The Mumonkan Case 29, translation by Robert Aitken
And if humankind becomes extinct, and no one is around to pray,
Does God still exist?