Woodward and Devonis in their article, Toward a New Understanding of Scientific Change: Applying interfield theory to the history of psychology, extend the examples of interfield theories (such as those discussed in Darden & Maull, 1977) to cases from the history of psychology. In addition, they develop a comprehensive model of scientific change that they label "interfield science". Their "interfield science" aims at being a more comprehensive model than did the generalizations from the cases discussed by Darden and Maull; also, it is more pluralistic in advocating diverse kinds of relations among areas of science, including both interfield bridges and reduction. This commentary will focus on two points: 1) another study of interfield theories in psychology, and 2) the contrast between interfield and interlevel analyses, on the one hand, and reduction analyses, on the other.