The "but" is that there are other ways we could model imperfect competition, and, as we're going to see today, they yield different answers.

但是"是指,通过其它方式也能获得不完全竞争模型,并且,就像我们今天会看到的,它们会产生不同的结论

耶鲁公开课 - 博弈论课程节选