I certainly am much more optimistic about odds than a lot of people on certain topics. For example, the odds I give of at least one successful business happening because of something in this post are quite divergent from the person who placed odds the other direction, who is someone whose intelligence I respect a lot.

Given the divergent opinions, I asked him to make predictions for several different specific/measurable outcomes for various scenarios, and we discussed what updates that he'd make to his belief system if the results are as I predict.

I highly recommend doing this - if people commit to updates based on probability they assign before hindsight bias, the updates are much more extreme than they otherwise would be; the updates might not happen much at all without the person really getting clear about how much they disagree ahead of time.