My feeling is that the first question is only answerable by the market. That answer is never certain. You're only as sure as the effort/time/money you put into

My feeling is that the first question is only answerable by the market. That answer is never certain. You're only as sure as the effort/time/money you put into reaching the market to answer it. The second question is easier to get an estimate for, but you probably defined your market incorrectly (especially if you're not solving your own problem). The last one is sticky. It reminds me of BSG. The human capacity for self-deception is without bound... That said, it's still useful to struggle with these questions periodically. Startups are all about the fight. You'll never have certain answers. Measure, learn, and adjust.