 This reply is adequate only if it is true, as Popper assumes, that singular existential statements will always do the work of bridging the gap between a universal theory and a prediction. Hilary Putnam in particular has argued that this assumption is false, in that in some cases at least the statements required to bridge this gap (which he calls “auxiliary hypotheses”) are general rather than particular, and consequently that when the prediction turns out to be false we have no way of knowing whether this is due to the falsity of the scientific law or the falsity of the auxiliary hypotheses. The working scientist, Putnam argues (Putnam 1974; see also the 1991 reprinting with its retrospective note), always initially assumes that it is the latter, which shows not only that, but also why, scientific laws are, contra Popper, highly resistant to falsification, as Kuhn (1962) and Lakatos (1970, 1978) have also argued.