Medical marijuana is now legal in more than half of the country. The cities of Denver, Seattle, Washington and Oakland, Calif., have also decriminalized psilocybin (the psychedelic element in “magic mushrooms”). Oregon went one step further, decriminalizing all drugs in small quantities, including heroin, cocaine and methamphetamine.

Attitudes toward drugs have changed considerably over the years. But the question of whether all drugs should be legalized continues to be contentious. How much have attitudes toward illegal drugs changed? And why?

This week, Jane Coaston talks to Ismail Ali, the policy and advocacy director for the Multidisciplinary Association for Psychedelic Studies, and Jonathan P. Caulkins, a professor of operations research and public policy at Carnegie Mellon University’s Heinz College, about the pros and cons of legalizing all drugs.

Mentioned in this episode:

“Is there a Case for Legalizing Heroin?” by Benjamin Wallace-Wells in The New Yorker

“The Drug-Policy Roulette” by Jonathan P. Caulkins and Michael A.C. Lee in the National Affairs Summer 2012 edition

“Michael Pollan’s ‘Trip Report,’” on The New York Times Opinion podcast “Sway”