The idea of giving poor people cash, no strings attached, is "very unappealing" for most donors, admits economist Michael Faye -- but it's still one of the best ways to help the poor. Michael and Julia discuss the philosophy behind his organization (GiveDirectly), the evidence we have so far about cash transfers as an anti-poverty intervention, and the various concerns people have about it: How long-lasting are the effects? Does it make recipients less likely to work? Does it cause inflation?

Humanity could thrive for millions of years -- unless our future is cut short by an existential catastrophe. Oxford philosopher Toby Ord explains the possible existential risks we face, including climate change, pandemics, and artificial intelligence. Toby and Julia discuss what led him to take existential risk more seriously, which risks he considers underrated vs. overrated, and how to estimate the probability of existential risk.

Julia and guest Vitalik Buterin (creator of the open-source blockchain platform Ethereum) explore a wide range of topics, including: Vitalik's intellectually honest approach to leadership, why prediction markets appear to be biased in favor of Trump, whether it was rational to invest in Bitcoin ten years ago, Vitalik's defense of life extension research against its critics, and more.

Julia and social psychologist Jonathan Haidt (The Righteous Mind) discuss his moral foundations theory and argue about whether liberals should “expand their moral horizons” by learning to think like conservatives. Julia solicits Jon’s help in understanding her disagreement with philosopher Michael Sandel, in episode 247, over the morality of consensual cannibalism.

Matt Yglesias talks about One Billion Americans, his book arguing that it’s in the United States’ national interest to dramatically boost its population, by expanding immigration and having more babies.

Matt and Julia also discuss arguments for and against the “YIMBY” movement, which pushes for building more housing; what they’ve both learned from reflecting on their misguided support for the Iraq War in 2003; and why (and how) Matt is trying to be more of a rationalist.

The traditional story about reason is that it evolved to help humans see the world more clearly and (thereby) make better decisions. But on that view, some mysteries remain: why is the human brain so biased? Why are we so much better at defending our pre-existing views than at evaluating new ideas objectively?

In this episode of Rationally Speaking, Julia talks with guest Dan Sperber, professor of cognitive and social sciences, who is famous for advancing an alternate view of reason: that it evolved to help us argue with our fellow humans and convince them that we're right.

Dan Sperber is a social and cognitive scientist. His most influential work has been in the fields of cognitive anthropology and linguistic pragmatics. Sperber currently holds the positions of Directeur de Recherche émérite at the Centre National de la Recherche Scientifique and Director of the International Cognition and Culture Institute.

This episode of Rationally Speaking features philosopher Kenny Easwaran, who delves into the notorious "Newcomb's Paradox" -- the puzzle about which it was once said, "To almost everyone it is perfectly clear and obvious what should be done. The difficulty is that these people seem to divide almost evenly on the problem, with large numbers thinking that the opposing half is just being silly." Kenny and Julia explore how Newcomb's Paradox is related to other puzzles in decision theory, like the Prisoners' Dilemma; what its implications are for free will; and what Kenny calls the "deep tragedy" at the heart of rationality.

Kenny Easwaran is an Associate Professor in the Philosophy Department at Texas A&M University. He works on several topics relating to epistemology and decision theory, and the role of probability in helping to understand these and related concepts.

You might expect that professional ethicists -- people whose job it is to determine which behaviors are ethical and why -- would behave more ethically than other people. You'd be wrong! This episode features philosopher Eric Schwitzgebel , who is well known for his work studying whether experts in ethics live up to their own standards. He and Julia discuss why the answer is "no," and explore questions like, "How do you decide how moral you're going to try to be?"

Eric Schwitzgebel is a Professor of Philosophy at University of California at Riverside. He is the co-author (with Russell T. Hurlburt) of Describing Inner Experience?: Proponent Meets Skeptic and blogs at The splintered Mind.

For several centuries, historians have tried to answer the question: "Why is Western Europe (and later, North America) the dominant world power?" Past explanations cited culture, or "great men" who influenced the course of history. Stanford historian Prof. Ian Morris casts doubt on those explanations, instead taking a data-driven approach to the question that attempts to measure "social development" over history and find explanations for it. In this episode of Rationally Speaking, Julia delves into Morris' method and conclusions, and asks: can we make causal inferences about history?

Ian Morris is Willard Professor of Classics and Fellow of the Archaeology Center, Stanford University. He is a historian and archaeologist. He has excavated in Britain, Greece, and Italy, most recently as director of Stanford's dig at Monte Polizzo, a native Sicilian site from the age of Greek colonization. He is also the author of a number of books, among them: "Why the West Rules--for Now". "War! What Is It Good For?", and "Foragers, Farmers, and Fossil Fuels."

A controversial field of research is "gain-of-function," in which scientists take a virus (like a strain of flu) and attempt to make it more dangerous, for example by making it transmissible in mammals when it had previously been solely an avian flu. The motivation is to learn how viruses might mutate in nature so that we can be prepared -- but what if those engineered "superbugs" escape the lab and start a pandemic? In this episode of Rationally Speaking, Harvard professor of epidemiology Marc Lipsitch argues that the risks outweigh the benefits, and that we should halt gain-of-function research as soon as possible.

Marc Lipsitch is Professor of Epidemiology with primary appointment in the Department of Epidemiology and a joint appointment in the Department of Immunology and Infectious Diseases. He directs the Center for Communicable Disease Dynamics, a center of excellence funded by the MIDAS program of NIH/NIGMS. He is also the Associate Director of the Interdisciplinary Concentration in Infectious Disease Epidemiology.

In this episode, economist Robin Hanson explains the signaling theory of human behavior: That our motivations for our choices, about school, shopping, medical care, and so on, evolved primarily to shape other people's perceptions of us. In the process Robin and Julia discuss what makes a good theory: How to decide what you should (a priori) expect to see, and why simplicity is a virtue.

Robin Dale Hanson is an associate professor of economics at George Mason University and a research associate at the Future of Humanity Institute of Oxford University. He is known as an expert on idea futures and markets, and he was involved in the creation of the Foresight Exchange and DARPA's Future MAP project. he blogs at Overcomng Bias.

Common wisdom holds that the world is getting more violent, but is that really true? Leading skeptic Michael Shermer, professor and author of many books on science, morality and skepticism, argues to the contrary. Shermer's thesis in his recent book, "The Moral Arc: How Science Leads Humanity Toward Truth, Justice, and Freedom," is that as science has advanced our understanding of the world, we have become more willing to expand our circle of empathy beyond our own provincial "tribes," and more able to design our societies to encourage human flourishing.

Dr. Michael Shermer is the Founding Publisher of Skeptic magazine, a monthly columnist for Scientific American, a regular contributor to Time.com, and Presidential Fellow at Chapman University. His new book is The Moral Arc: How Science and Reason Lead Humanity Toward Truth, Justice, and Freedom.

Companies like Twitter and Facebook are increasingly willing to ban users -- and even if you agree with their decisions, is it worrying that a few companies have so much power? Julia discusses with Julian Sanchez, expert on tech and civil liberties.

In this episode of Rationally Speaking, Caltech physicist Sean Carroll describes an "embarrassing" state of affairs in modern physics: that we still don't know how to interpret quantum mechanics, almost a century after its discovery. Sean explains why he thinks the "Many Worlds Interpretation" (MWI) is the most plausible one we've got, and Julia explores his thoughts on questions like: Can MWI be tested? Is it "simpler" than other interpretations, and why? And does MWI threaten to destroy our systems of ethics?

Sean Michael Carroll is a research professor in the Department of Physics at the California Institute of Technology. He is a theoretical cosmologist specializing in dark energy and general relativity.

Coleman Hughes explains why he favors a "colorblind" ideal and why the "race-conscious" camp disagrees with him. Coleman and Julia also discuss whether reparations are just, and what counts as racism.