I was wondering how Berkeley knows anything exists without him sensing it, like another person. There is no test to know if some one exists without use of the senses is there? That is the only way we take as humans take in knowledge and learn. So if I were to loose all of my senses (such as sight, hearing, touch, taste etc.) how would I know that anything exists except for myself. Just because I can think or move is not proof enough that anything except for my self to exist.