"If a tree falls in a forest and no one is around to hear it, does it make a sound?" is a philosophical riddle that raises questions regarding observation and knowledge of reality. History Philosopher George Berkeley, in his work, A Treatise Concerning the Principles of Human Knowledge, 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 ...