Interdisciplinary integration has fundamental limitations. This is not sufficiently realized in science and in philosophy. Concerning scientific theories there are many examples of pseudo-integration which should be unmasked by elementary philosophical analysis. For example, allegedly over-arching theories of stress which are meant to unite biology and psychology, upon analysis, turn out to represent terminological rather than substantive unity. They should be replaced by more specific, local theories. Theories of animal orientation, likewise, have been formulated in unduly general terms. A natural (...) history approach is more suitable for the study of animal orientation. The tendency to formulate overgeneral theories is also present in evolutionary biology. Philosophy of biology can only deal with these matters if it takes a normative turn. Undue emphasis on interdisciplinary integration is a modern variant of the old unity of science ideal. The replacement of the ideal by a better one is an important challenge for the philosophy of science. (shrink)