 The separation terminology is due to Smets et al., who relate it to separation principles in point-set topology. In terms of the epistemological interpretation of point-set topology from  Section 3.2,  we have \(H_1 \lt H_2\) if and only if every complete data sequence for \(H_1\) is a boundary point for the data sequences of \(H_2.\) In an epistemologically resonant phrase, Genin and Kelly say that hypothesis \(H_1\) “faces the problem of induction” with respect to \(H_2\) whenever \(H_1 \lt H_2\). This is because whenever \(H_1\) is correct, a reliable learner will have to take an “inductive leap” and conjecture \(H_1\) although any finite amount of evidence is also consistent with \(H_2\).