The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody. This is Idea #19, "Probability and Randomness." In which we accept that none of us is Laplace's Demon, and in the real world we act under conditions of incomplete information, necessitating a turn to probabilistic reasoning. We talk a bit about what that it, how it works, and how it applies to statistical mechanics. My web page: http://www.preposterousuniverse.com/ My YouTube channel: https://www.youtube.com/c/seancarroll Mindscape podcast: http://www.preposterousuniverse.com/podcast The Biggest Ideas playlist: https://www.youtube.com/playlist?list=PLrxfgDEc2NxZJcWcrxH3jyjUUrJlnoyzX Blog posts for the series: http://www.preposterousuniverse.com/blog/category/biggest-ideas-in-the-universe/ Background image: https://www.theaa.ie/travelhub/las-vegas/ #science #physics #ideas #universe #learning #cosmology #philosophy #probability #bayes