The "complexity" problem dealt with in the debate "holism vs riductionism" has given rise more than once to proposals that are radically opposed. Such a problem includes scientific spheres which differ greatly one from another: from physics to biology, ecology to ecology, psychology to sociology, and, last but not least, to epistemology. Not until the terms used in that debate have been clarified by a preliminary explanation will we be able to free the analyi of the main themes present in each of the specific scientific spheres. The necessity of the introduction of a methodologica assumption in order to discriminate between semantic, metaphysical, methodologica, and epistemological domains is not always noticed. Such an absence of awareness leads to misunderstandings caused by the facts that the same terms are inadvertently used as referring to different semantic spheres. Above all it overshadows the fact that the terms in the comparison are not simply "the holism" and "the reductionism", but "the holisms" and the "reductionisms".