What is 'Unperceived existence' in Philosophy?

This refers to a philosophical question regarding the nature of reality and human perception. It asks whether something that is obvious to the human senses exists at all when it is not being observed by someone. It is expressed through the question, “If a tree falls in a forest and no one is around to hear it, does it make a sound?” The idea was proposed by Irish philosopher George Berkeley in his 1710 book called A Treatise Concerning the Principles of Human Knowledge .