 Here then is the methodological analogy and link between the principle of induction, conventions in the sense of apparent hypotheses and verifiable hypotheses. All are guided by experience without being (entirely) experimental, and all involve presupposed categories, natural hypotheses or a given structure (Folina 2020). Verifiable hypotheses employ conventional elements in the generalization process and may presuppose the (empirical) principle of induction. Geometrical conventions are apparent hypotheses guided by the experience of muscular sensations and involve the category of groups. Both these sorts of hypotheses, verifiable and apparent, employed in physics and geometry, are in Poincaré’s hierarchy of sciences framed on the one hand by a priori principles and natural hypotheses that are tools both for mathematicians and experimenters, and on the other hand, by indifferent hypotheses and physical principles. The indifferent hypotheses are conventional (in the ordinary sense) stipulations of ontological entities—mechanical models that increase our theoretical insight, while the physical principles are either verifiable hypotheses elevated by decree beyond the crucible of experiment or well-founded with respect to the network of actual science.