The following paper is intended as an exercise in "friendly criticism" of one of Harvey Siegel's and Mike Smith's ("Knowing, Believing and Understanding", this volume). I'm in substantial sympathy with the general thrust of their paper and my remarks merely provide some criticism of their discussion's conceptual coherence and clarity and a correspondingly slightly adjusted version of what they have to say. My focus is limited to the conceptions of knowledge, belief and understanding and their inter-relationships in terms of which they offer suggestions to science educators.