 Many regard set theory as in some sense the foundation of mathematics. It seems that just about any piece of mathematics can be carried out in set theory, even though it is sometimes an awkward setting for doing so. In recent years, the philosophy of set theory is emerging as a philosophical discipline of its own. This is not to say that in specific debates in the philosophy of set theory it cannot make an enormous difference whether one approaches it from a formalistic point of view or from a platonistic point of view, for instance.