 Shapiro and Polger (2012) build upon Shapiro’s account of the complexity of actually testing for scientifically-justified multiple realization. They insist that these actual details render the significance of multiple realization far more dubious than philosophers of mind typically suppose. They introduce explicit criteria to capture the common assumption that multiple realization requires not merely differences between realizing kinds, but “differently the same”: the features of entities A and B that lead them to be classified differently by the realizing science S2 “must be among those that lead them to be commonly classified” by the realized science S1 (2012: 282, criterion iii). This explicit criterion rules out the popular assertion that camera eyes versus compound eyes, with different photoreceptive chemicals in their retinal cones, is a genuine (empirical) instance of multiple realization. Considered coarsely, such eyes are doing the same thing in the same way, so they’re not “differently the same”. Considered finely, the two kinds of eyes are sensitive to different ranges and peaks of spectral stimulation, so they’re “differently different, not differently the same” (2012: 283–284).