I think that the original question could have been improved, but contrary to a number of comments on the question and here I think that the psychological side of subject is very appropriate for an aviation site.
How should I as a copilot prior to a commercial flight address my concerns that my captain is unfit to fly?
You can take the legalistic approach, but the part that people struggle with is how to address the captain in such a case. There are no black and white rules there, but I am sure there are people here that have valuable advise about things you should do and not do under these circumstances.
Lack of proper communication between crew members is a major cause of incidents in aviation, and it is known that in many cases the psychological and ethical issues around addressing someone with higher authority are the root cause there. This question shows that these situations are not limited to the flight deck, but also occurs outside of the pointy end of the aircraft.
For comparison, on academia.stackexchange.com similar ethical questions arise every now and then and the answers provided there seem to be quite helpful.