Not enough people know about the Mohists, a strikingly modern group of Chinese philosophers active in 479-221 BCE. This episode features Chris Fraser, expert on Mohism and professor of philosophy at the University of Hong Kong. Chris and Julia discuss how the Mohists put their philosophy into practice and got Chinese leaders to hold off on starting wars; how their philosophy was similar to and different from modern consequentialism; why their movement died out, and what modern groups like Effective Altruists can learn from their story.

This episode features the hosts of "Ask a Mathematician, Ask a Physicist," a blog that grew out of a Burning Man booth in which a good-natured mathematician (Spencer Greenberg) and physicist (Seth Cottrell) answer people's questions about life, the universe, and everything. Spencer and Seth discuss the weirdest and most controversial questions they've answered, why math is fundamentally arbitrary, Seth's preferred alternative to the Many Worlds Interpretation of quantum physics, how a weird group of parapsychologists changed the field of physics, and whether you could do a Double Slit Experiment with a Cat Cannon.

This episode features political scientist Rob Reich, author of "Just Giving: Why Philanthropy is Failing Democracy, and How it Can Do Better". Rob and Julia debate his criticisms of philanthropy: Does it deserve to be tax-deductible? Is it a violation of the autonomy of recipients to attach strings to their charitable gifts? And do philanthropists have too much power in society?

This episode features Peter Eckersley, an expert in law and computer science, who has worked with the Electronic Frontier Foundation and the Partnership on AI. Peter and Julia first delve into some of the most fundamental questions about privacy: What are the risks of losing privacy? Do we have more to fear from governments or industry? Which companies do a good job of protecting their users' privacy? Are there tradeoffs between supporting privacy and supporting competitive markets? Next, they discuss Peter's work measuring recent progress in AI, and debate to what extent recent progress is cause for optimism.

Economist Jason Collins discusses problems with behavioral economics: reliance of governments, suspicious number of cognitive biases, problematic 'nudges'. Also explores flaws in neoclassical economics, exploitation by marketers, limitations of naming biases, and concerns about pendulum swinging too far in favor of behavioral economics in policymaking.

In this episode, economist Chris Auld describes some common criticisms of his field and why they're wrong. Julia and Chris also discuss whether there are any good critiques of the field, and whether economists think that people with an addiction to alcohol or drugs are behaving rationally.

Aviv Ovadya, an expert on misinformation, talks with Julia about the multiple phenomena that get lumped together as "fake news." For example, articles that are straightforwardly false, misleading, or artificially created (think "Deepfakes," videos that make a politician appear to say something he didn't say). Which of those problems are more dangerous for our civilization? Are any of them tractable? And what might a solution look like?

On this episode of Rationally Speaking, professor Diana Fleischman makes the case for transhumanist evolutionary psychology: understanding our evolved drives, so that we can better overcome them. Diana and Julia discuss sexual preferences, jealousy, and other drives -- how immutable are they? How do we know? And how would it change society, if we could change the distribution of people we find attractive, or normalize new relationship structures such as polyamory?

This episode features Anders Sandberg, a researcher at Oxford's Future of Humanity Institute, explaining several reasons why it's valuable to think about humanity's long-term future. Julia and Anders discuss the common objection that we can't predict or steer the future, and explore whether people really care if humanity dies out.

This episode features physicist Anthony Aguirre discussing Metaculus, the site he created to crowd-source accurate predictions about science and technology. For example, will SpaceX land on Mars by 2030? Anthony and Julia discuss details such as: why it's useful to have predictions on questions like these, how to measure Metaculus' accuracy, why Anthony chose not to run it like a traditional prediction market, and how to design incentives to reward good forecasters.