What kinds of contact can the mind have with the world?  Can we know how the world is in itself, or can we only know shadows of the world in our own minds?  Are we trapped behind a veil of our own mental states?  Is there a world outside my mind – or our minds – at all?  John and Ken tackle the big questions of perception, the external world, and the nature of reality, with Howard Robinson from the Central European University, author of From the Knowledge Argument to Mental Substance: Resurrecting the Mind.