This chapter proposes that singular compositional abduction has four features shared by at least many other instances of abduction: (1) abduction is sometimes used for confirmation, (2) abduction is sometimes used to postulate entities that are qualitatively distinct from the entities cited in the supporting evidence, (3) abduction may rely on background beliefs, and (4) abduction is sometimes used to postulate entities that are not directly empirically detected. It also indicates why scientists take abduction to be truth conducive. It shows how compositional abduction may serve as an alternative to the theory of hypothetico-deductive confirmation. Finally, it suggests a broad range of scientific cases in cognitive science that might be understood in terms of singular compositional abduction.

This chapter provides the second case study of the use of singular compositional abduction based on scientific attempts to determine the biological basis of the Hermann grid illusion. First reported by Ludimar Hermann in 1872, the illusion was first explained in terms of local points of simultaneous contrast. In 1961, Gűnter Baumgartner fleshed out the proposal arguing that the illusion might be explained in terms of activity instances of retinal ganglion cell firings. Further, Lothar Spillman performed experiments intended to support this proposal, whereas Jeremy Wolfe, Peter Schiller, and Christina Carvey described experiments meant to challenge it.