Chmess, for those of you who haven't heard, is just like chess - except the king can move two squares in either direction. As Daniel Dennett has pointed out, Chmess provides a rich source of a priori truths to explore. However, the a priori truths of chmess are not particularly worthy of exploration. Dennett's challenge of Chmess is to explain the difference between describing the a priori truths of Chmess and practicing philosophy.
Most other disciplines in the university do not face the challenge of Chmess. There is no doubt that there are physical, biological, and social facts, and understanding them clearly can lead to human flourishing. The other humanities don't worry about the challenge of Chmess, for a very different reason. Most humanists do not see their central project as uncovering some domain of truths that have hitherto gone unnoticed. Rather, they see their role as galvanizing students into challenging what they have previously taken for granted, in an attempt to help them construct a value system that is genuinely their own. If an autonomous life is one that is the product of one's own free, informed deliberations, then the goal of the humanities thus conceived is to help young people gain autonomy. The process of challenging and breaking down assumptions and investigating different systems of thought is a necessary step in this process, and here the sciences can only play an indirect role.
In philosophy, as much as any other discipline, one engages in the practice of investigating alternative conceptual structures, be they systems of value or systems of belief. Such investigations may seem like theorising about Chmess, if we conceive of philosophy as a science. But if we regard philosophy instead as an activity intended to help those who learn it acquire the resources to lead a dignified life, it quite clearly does not.