  Against the backdrop of a social media reckoning, this paper seeks to
demonstrate the potential of social tools to build virtuous behaviours online.
We must assume that human behaviour is flawed, the truth can be elusive, and as
communities we must commit to mechanisms to encourage virtuous social digital
behaviours. Societies that use social platforms should be inclusive, responsive
to evidence, limit punitive actions and allow productive discord and respectful
disagreement. Social media success, we argue, is in the hypothesis. Documents
are valuable to the degree that they are evidence in service of, or to
challenge an idea for a purpose. We outline how a Bayesian social platform can
facilitate virtuous behaviours to build evidence-based collective rationality.
The chapter outlines the epistemic architecture of the platform's algorithms
and user interface in conjunction with explicit community management to ensure
psychological safety. The BetterBeliefs platform rewards users who demonstrate
epistemically virtuous behaviours and exports evidence-based propositions for
decision-making. A Bayesian social network can make virtuous ideas powerful.
