The term psychology refers both to an institutional discipline and to a subject matter. Henriques, in his article “Psychology Defined” (this issue) , emphasizes the second reference, and its focus can be sharpened by taking into account the first reference. On the one hand, epistemic progress in science is a dynamic process, which, as often as not, cuts across institutional divisions. However, on the other hand there are some problems of disunity that solely concern the institution. That the latter falls within the scope of the Tree of Knowledge is illustrated in how Henriques' “Justification Hypothesis” sheds light on the nature of institutional disunity. © 2004 Wiley Periodicals, Inc. J Clin Psychol.