Streszczenie:
Different versions of the so called underdetermination principle, proposed in the philosophy of science by W. Newton-Smith, M. Hesse, E. McMullin, accentuate that for any scientific theory T1, consistent with a set of accessible empirical data D, one can always introduce a set of alternative theories T2 Tn which differ in their content but remain consistent with the data D. In epistemological comments developed by supporters of the postmodernist philosophy, the underdetermination principle is interpreted as an expression of the internal irrationality of science. The paper provides criteria which permit to accept both the critical version of the underdetermination principle and a modified understanding of the rationality of science.