During the preparation period for European Union membership, educational discourse in Eastern European countries has attempted to integrate into the general European framework. Characteristic to that period in Eastern European countries, particularly in early 1990s, has been uncritical adoption of different and often contradictory Western educational concepts. Each of these concepts attempts to embrace theoretical and practical field in its own terms. Accumulation of the contradictory concepts and terminological vagueness has become to inhibit constructive educational discussion within these countries. This has lead to the need to clarify the base on which the educational concepts should be legitimated. In current paper, I argue for stronger epistemological consideration in adoption of Western educational concepts into educational discourse of Eastern European countries. I claim that mostly the adoption of educational concepts in Eastern European countries is legitimated by socio- historical arguments emanated from one- sided attachment to one or another Anglo- Saxon or Continental European theoretical concept. By example of teacher education curriculum in Tartu University, Estonia, I demonstrate the arguments used for legitimation and denomination of its core disciplines: Educational Theory, Educational Theory and Educational Developmental Psychology and General Didactics. I show the mutual inconsistency and haphazard overlap of the content of labeled as Educational Theory, mostly based on theories with Anglo- Saxon roots, and General Didactics, mostly based on German educational theories. Published and electronically available teaching material and annotations of the courses are used as research material. I conclude that arguments derived from within a particular educational concept itself, can't be sufficient for emulation of the concept in any Eastern European country. Neither are the socio- historical arguments, like historical and cultural closeness, sufficient, though they are necessary. Rational epistemological consideration of the concepts is needed. To generalize from the case of Eastern European countries, holistic concept and incommensurability thesis of theories via Kuhn should be rejected on pragmatic reasons: we are forced to choose between already existent rival concepts, each with its own terminology. While making educational decisions, denominating the educational disciplines for curriculum and labeling the practitioners on certain educational field, these contradictory concepts can't be handled equally. Sooner or later, we are forced to eliminate some concepts. For doing that, we need ground accepted as commonly as possible. Using the example of previously denominated disciplines in teacher education curriculum of Tartu University, I show how the principles of critical rationalist epistemology of Popper can be applied for selection between the educational concepts. I side with Popper that frameworks of different scientific concepts can and should be rationally evaluated over the boundaries of language and cultural context. I conclude that Popperian principle of mutual criticism and elimination of errors should be engaged for assessing epistemological validity of educational concepts.