Harry Collins's project in the sociology of knowledge – the Empirical Programme of Relativism (EPOR) – is inspired by the Strong Programme. However, Collins rejects the idea that explanation should be causal, and eschews explanation of the genesis of theories: only their reception can be accounted for. EPOR is divided into three stages: (1) Demonstrating the "interpretative flexibility" of experimental data. (2) Showing the local social mechanisms by which closure is effected. (3) Linking the local closure mechanisms to wider social forces. Collins illustrates these stages with a number of case studies. His main result is what he terms the "experimenters regress", to the effect that the outcomes of experiments are forever open to rival interpretations, since there is no rigorous methodological algorithm to decide the issue. Instead, the matter is decided by social forces. Like the Strong Programme, Collins reinforces his position with philosophical arguments culled from Wittgenstein's works, among others. In so doing, Collins invites the same problem concerning indeterminacy of meaning of scientific theories that infected Bloor's position. His relativism also generates a problem of reflexivity. Collins tries to tackle this problem by invoking the notion of "meta-alternation", but without success. Recently, Collins has initiated what he calls the "Third Wave" of STS, in which the normative stance of the movement is made explicit and moved to the forefront.