How do we know?

When it comes to scientific knowledge, we’re selective about who and what we believe. But, how do we get to a place of knowing? We hear from people who were believed — and those who weren’t — to find out what made the difference.

Also heard on this week’s show:

• UPenn Philosophy professor Michael Weisberg explains what scientific knowledge is, and how we acquire it.
• We explore the history of mental illness in gun laws, and whether psychiatrists are good at determining who will be violent.
• Writer Lydia Pyne describes the enduring mystery of the longest-running hoax in science history – and why so many people believed it.