 The negative heuristic of the programme forbids us to direct the modus tollens at this “hard core”. Instead, we must use our ingenuity to articulate or even invent “auxiliary hypotheses”, which form a protective belt around this core, and we must redirect the modus tollens to these. It is this protective belt of auxiliary hypotheses which has to bear the brunt of tests and gets adjusted and re-adjusted, or even completely replaced, to defend the thus-hardened core. (FMSRP: 48)