Can we know whether anybody else exists? Are we the only conscious being that exists? Is everything else a projection? Some say so. Solipsism is the belief that everything external to our mind is unsure, and that it is impossible to know whether anything outside ourselves is real.
Gorgias the Sophist was the first philosopher to entertain solipsism and scepticism, and Descartes, in his meditations, wrote that we can only know that we ourselves exist. Solipsism can lead to depersonalization disorders and indifference to the world-if it doesn’t exist, why care for it? However, a solipsistic world view is bound to crumble when surrounded with other people, otherwise permanent detachment, and maybe even madness, will ensue.