Although researchers agree on the importance of validity, they have not yet reached a consensus on what validity consists of. This article traces the historic trajectories of validity theory development in three research traditions: psychometrics, experiment in social settings, and animal models of psychiatric disorders, showing that the multiplicity in the concept of validity is shaped by its multiple historic trajectories and reflects the diversity of practices and concerns in different research traditions. I argue that specifying validity of what target practice and for what purpose in discussions helps to connect validity to its rich context that gives rise to its specific meaning and relevance.