I estimate a 0.1% chance he intended it to be an uninformative prior.
People start with this prior in the examples you gave when they are completely uncertain and have no better mental model. It is not a good starting point for an event that has never happened and can only happen once.
alt Hacker News
People start with this prior in the examples you gave when they are completely uncertain and have no better mental model. It is not a good starting point for an event that has never happened and can only happen once.