According to Holton (1981), the themata are irrefutable and implicit ontological conceptions, in the form of couples of opposition: unity versus diversity, complexity versus simplicity... We identify the intervention of such metaphysical presuppositions in the academic work of nine scholars involved in the french field of sports sciences research. Moreover, from interviews "tales of research", we try to understand which motivates the thematic choices by the researchers. Two hypotheses are tested: firstly, a scholar would prefer a given thematic option because this one allows him to invest intimate values and meanings, in reference to his peculiar history; secondly, as far as the themata recover from the symbolic thought, the thematic choices depend on an iconographic rationality where the pictures have a spontaneous power of evocation on the scientist. Although the thematic commitments appear as the result of motivated choices, they remain unverifiable, what obliges to discuss of their modalities of participation in the scientific reasoning. We present two pragmatic positions which suggest to assess not the a priori validity of the themata but their a posteriori fecundity.