The present volume aims at giving a discussion ot the problems ot reductionism in contemporary life sciences. It contains six papers which deals with reduction/reductionism in different fields ot biological research. Also, the holistic perspective, 1. e. the systems view, is discussed in some ot the papers. The message ot this discussion Is that - whereas reductionism is indeed an important strategy - the systems approach is needed. It is argued by some ot the authors that organisms are complex systems and not just heaps of molecules, 50 that the analytical method does not suffice. Recent developments in systems theory offer the possibility to install a more comprehensive view ot living systems what can be seen particularly in the field ot evolutionary biology. It is true that any organismic activity is molecular, this is to say that it is based on molecular mechanisms. But it is also true that the whole organism displays certain patterns ot behavior which are not just molecular. Any organism can be described as a system ot different levels ot organization different levels ot order and complexity - and it is important, theretore, to study all ot the organizational levels and to see their peculiarities. It should be obvious, however, that there is not one problem ot reduction/reductionism, but that there are many problems linked together and that these problems appear at different levels ot biological research and bio philosophical reflections.