Recently, some teachers have launched proposals for teaching physics by starting from thermodynamics rather than from mechanics. Such proposals are included in Mach's thesis, according to which thermodynamics is more basic for theoretical physics than mechanics. The past history of such a thesis is quickly sketched. Then, by recent results in theoretical physics, it is qualified in a new, modern version. As such it appears as an instance of a general conflict between two radically different ways to produce theoretical physics. The conflict results from two different options, about both the kind of mathematics and the kind of the organization of the theory. After such a general illustration of the great relevance of history of physics for physics teaching, the cultural bounds of such proposals are recognized and discussed.