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

"If a tree falls in a forest and no one is around to hear it, does it make a sound?" is a philosophical thought experiment that raises questions regarding observation and knowledge of reality. File:If a tree falls in the forest. Jpg|thumb|left|This coosy with the proverbial question has raised deep philosophical questions .

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."1 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: "Tease 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. Some years later, a similar question is posed. It is unknown whether the source of this question is Berkeley or not.