This document summarizes a presentation by Ivan Oransky on how we know what we know in health sciences and challenges to creating knowledge. It notes that retractions are on the rise, studies are often wrong, and "winner-takes-all" incentives can encourage dishonest practices. It discusses how anonymous whistleblowers, aggressive blogs, journals listening to post-publication peer review, and altmetrics are helping address these issues. The presentation cautions about positive publication bias and confirmation biases affecting knowledge, and calls for publishing all data and more conditional drug approvals to improve reliability of knowledge over time.