I’ve got a question for you: Does the computer you’re reading this on right now exist? It does, huh? Okay, prove it. You say it exists because you can touch and see it. So what? Maybe you’re just a brain in a vat, being fed raw sense data for an imaginary world. Freaking out yet? No, you say, because that’s the plot of the Matrix and that movie is, like, super old. Okay, fair. But mind-melting questions like this aren’t just the stuff of movies. In fact, they are at the core of the branch of philosophy known as metaphysics, which asks questions about what exists in the world and what that stuff is like. Metaphysics has been a key part of philosophy from the very beginning and continues to be a major area of study today.

“St Thomas Aquinas” by Lawrence OP is licensed with CC BY-NC-ND 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-nd/2.0/. https://www.flickr.com/photos/35409814@N00/40626309662 

“Aristotle” by Nick in exsilio is licensed with CC BY-NC-SA 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/2.0/. https://www.flickr.com/photos/33563858@N00/6884873348 

 “Bishop George Berkeley” by John Smibert, 1688 – 1751 is licensed with CC0 1.0. To view the terms, visit https://creativecommons.org/publicdomain/zero/1.0/. https://npg.si.edu/object/npg_NPG.89.25 

 “Immanuel Kant” by Special Collections at Johns Hopkins University is licensed with CC BY-NC-SA 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/2.0/. https://www.flickr.com/photos/41637252@N04/6767329877 

 “Friedrich Nietzsche: ‘Hoy no somos el mismo hombre de ayer y mañana volveremos a ser otro.'” by Antonio Marín Segovia is licensed with CC BY-NC-ND 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-nd/2.0/. https://www.flickr.com/photos/23465276@N04/19888500939