 The envisaged prediction (‘\(Bx\)’) no longer holds if a magnet neutralizes the effect of the weight (‘\(Mx\)’). This can be accounted for if the absence of the magnet is explicitly mentioned in the law. The problem is that the law must be complete with respect to all such factors that might prevent the breaking of the thread. The completeness condition requires that there are no further disturbing factors—i.e., it requires an exclusive cp-clause (see section 3) Canfield and Lehrer also present an argument for why these cp-clauses cannot be defined away, namely that any such attempt leads to an infinite regress of further cp-clauses.