Is the "theory" of the Matrix, or something along those lines, possible? We perceive the world with little signals sent to our brain, so couldn't those signals he rigged to, say, a machine? And everything happening around us is just in our heads? If you dissagree with this, what could you use to prove me wrong? ~Kris S.

I do not disagree with this, nor (I suspect) would most philosophers. The story of The Matrix is possible .But as long as we're talking about possibility, your situation might beeven worse than the one depicted in the movie. At least in the filmwe're all sharing the same, collective hallucination, but it might bethe case that you're the only one plugged into the Matrix.Perhaps you don't even have a full body; you might be just a brainfloating in a vat of nutrients and connected to a computer that isfeeding it electrochemical signals. In the Meditations ,Descartes famously considers an even more radical possibility: theentire material world could be an illusion. You could be a disembodiedghost dreaming that you have a body or a disembodied mind beingdeceived by a malicious and powerful demon into believing that there isa material world. Philosophers usually discuss outlandish thoughtexperiments such as these in order to raise questions about thepossibility of knowledge. Does knowledge...