PRIMUS-2012 proposes a phenomenographic foundation for the so-called problem method in teaching mathematics. It also breaks away one of the main myths about Inquiry Based Teaching: “class size should be small.” The article tells the story of a very non-standard, absolutely student-centered multivariable calculus course with 136 students. The version of the paper shared here, though very similar to the final version is not the final version. If you cannot access the published version from the publisher’s site, please do not hesitate to e-mail me.