During the period from its emergence in 1889 until the endof the Armistice period, the Committee of Union andProgress (CUP) underwent a transformation from "theseditious committee (cemiyet-i fesadiyye)" to "the sacredcommittee (cemiyet-i mukaddese)", and then back to“seditious" one. The role played by some former Unionistsduring the National Struggle and the early Republicanperiods was the source of the transfer of the perceptions ofUnionism to the political arguments in the Republicanperiod. Although the active political life of the Unionistswas terminated with the 1926 İzmir AssassinationAttempt, the perceptions proceeded within the languageshaping the studies on the CUP as socio-political andideological tools, almost without deviating from theirorigin. Over the course of time, the old perceptions aboutUnionism have been enriched with new conceptualapproaches that have been shaped by Turkey's currentconcerns and priorities; however, the perceptions aboutUnionism, which became apparent around excessivepolitical arguments with the aim of legitimizing orillegitimating the CUP during the Second Constitutionalera, have remained in existence as the result of havingundergone very little change until today. This continuity,has, on the one hand, influenced the efforts to understandthe political developments of the Constitutional eraretrospectively from the Republic of Turkey, while, on theother hand, led to the formation of the prejudices andgeneral acceptances in CUP studies by reinforcing thearguments stemming from the perceptions about Unionismduring the Constitutional era. Thus, it is significant toreconsider the rational context of the CUP historiographyin terms of the future course of CUP studies.