The purpose of this paper is to elaborate and comment on some themes related to construct validity, construct choice, and construct respecification in the Campbellian validity system. It is argued that Reichardt's [(2008, November). An alternative to the Campbellian conceptualization of validity. (Paper presentation). Evaluation 2008 Conference, Denver, CO, United States] assertion that construct validity and external validity are equivalent in the Campbellian system is not correct. The illustrated restricted kind of construct respecification given by Shadish, Cook, and Campbell [(2002). "Experimental and quasi-experimental designs for generalized causal inference." Houghton Mifflin] can be interpreted as part of causal explanation. Their illustrations of general respecifications, on the other hand, should not be considered construct respecifications, but be regarded instead as tentative basic explanations of study results. Choice of research problem or hypothesis -- as well as of the included constructs -- should be based on practical or theoretical needs in the research field.