Öz
Reasons of administrative acts are presented through various ways in laws; sometimes through strict statements, sometimes through indefinite terms. Although the reason of act has been explained by terms such as public order, public morality, public security, necessity, public morality, inefficacy etc., the first thing to carry out administration is to find out what the term means and then to solve whether the concrete case corresponds to the term or not. At this stage, drawing the lines of liberty of the administration is one of the most basic and contradictory issues. Turkish administrative doctrine generally does not perceive the notion of indefinite legal concepts as an issue which should be discussed in a more different way than the term of a discretionary act of the administration. However, German Administrative Jurists studiously distinguish the discretionary act and indefinite legal concepts from each other, and analyse each of them in a detailed way. Starting from this point of view, they attempt to reveal judicial control field. The approach of German Jurists has been increasingly influencing more judicial systems and it has emerged through learning from traumatic experiences during the historical process.