To learn and be certain that your assumptions are at least partially correct, one should strive for structured, scientific approach where your assumptions are tested in the real word.
In the context of a sustainable business model and startups one should talk to customers and go in dialogue or look at (potential) customer behaviours. A kin to asking players what they want in roleplaying games.
Reference
Ries, Eric. The Lean Startup: How Today’s Entrepreneurs Use Continuous Innovation to Create Radically Successful Businesses. 1st ed, Crown Business, 2011.
Highlights or timestamps
ideally validated learning, meaning learning through a scientific approach.
— ^cd9c3d from The Lean Startup
To begin the process of validated learning, you must come up with hypotheses about whether and how certain products will be successful in a given market
— ^7e0b9d from The Lean Startup
and only if they are validated by talking to customers can the start-up know it’s on the right track toward finding a sustainable business model.
— ^bc6bb9 from The Lean Startup