 This set theory interprets ZF. This is shown by demonstrating first that the discrete sets (and more particularly the (closed) sets of isolated points in the topology) satisfy an analogue of Replacement (a definable function (defined by a formula which need not be positive) with a discrete domain is a set), and so an analogue of separation, then by showing that well-founded sets are isolated in the topology and the class of well-founded sets is closed under the constructions of ZF.