EN
The article addresses the problem of scientific theory development treated as a specific form of discourse. This may be exemplified with two selected theoretical trends related to research migration - called in the text discourse of motive and discourse of adaptation - the authoress ties to show the logic of that form of discourse development. Important determinants shaping migration discourses are: - The historical moment of their formation together with the entire baggage of ontic assumptions and the empirical image of migration processes of that period; - Strong influence of doxa, from the very outset; - Regularity consisting of a gradual 'softening up' of initially elegant and unambiguous theory by adding new elements or detailing existing ones, as well as transferring the entire argument to another level of analysis; - The principles of any action in the scientific field force us to refer to already found heritage and to operate with legitimated language of existing theoretical concepts; - The narrowing by discourse of the field of possible conceivable intellectual alternatives in the scientific activity: you may accept an existing theory or critically refer to it but it is always the starting point (of course within a set paradigm, or - as in this case - one discourse trend); tertium non datur.