Solipsism is the philosophical idea that only one's own mind is sure to exist. Solipsism as an epistemological position holds that knowledge of anything outside one's own mind is unsure. The external world and other minds cannot be known, and might not exist outside the mind. As a metaphysical position, solipsism goes further to the conclusion that the world and other minds do not exist. As such it is the only epistemological position that, by its own postulate, is both irrefutable and yet indefensible in the same manner.
Contributions by Normxxx, Jon Awbrey, and Jiohdi.