In confirmatory factor analysis, the researcher first develops a hypothesis about what factors s/he believes are underlying the measures s/he has used (e.g., "Depression" being the factor underlying the Beck Depression Inventory and the Hamilton Rating Scale for Depression) and may impose constraints on the model based on these a priori hypotheses.
Besides his work in the area of phenomenology and philosophy in general, Reinach is credited for the development of a forerunner to the theory of speech acts by Austin and Searle: Die apriorischen Grundlagen des bürgerlichen Rechtes (The A Priori Foundations of Civil Law) is a systematic treatment of social acts as performative utterances and a priori foundations of civil law.
Alexander Laszlo & S. Krippner S. (1998) Systems theories: Their origins, foundations, and development. In J.S. Jordan (Ed.), Systems theories and a priori aspects of perception.