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A critical examination of Popper’s falsificationism as a methodological criterion of demarcation led to the development o f a supplementary means of distinguishing science from pseudo- science The discipline is made the unit of appraisal and its pattern o f historical development b used as the indicator of demarcation. Results of a test of this indicator against astrology and physical optics accord with our basic judgm ents of these disciplines. The indicator effectively reveals that scientific creationism is pseudo-science, and that evolutionary biology is genuine science. Three fundam ental approaches to scientific investigation, viz. v erificationism , falsificationism and m ulti-cornered testing (M CT) are contrasted. MCT is distinguished by competition between hypotheses, which makes it more informative than at least the naive versions of the other two approaches. While competition does not produce immediate victors, it does make demands on theories, which can be augmented by prescribing a series of independent tests. The comparative method implies the existence of two types of evidence. Common evidence is that which io predicted or explained by two or more rival hypotheses. Discriminatory evidence favours one rival over the others. It is argued that in both the fields of species biology and speciation there have been instances o f over-relying on common evidence, o f indistinctly defining alternative hypotheses, of ro t following their logical consequences and of not using exisiing discriminatory evidence to adjudicate between these hypotheses. Species concepts and definitions of modes o f speciation are evaluated. Normative principles are suggested for defining species and other important terms in evolutionary biology, and for testing species concepts and modes of speciation. The advantages and limitations o f a historical indicator of demarcation and the merits and principles of the comparative approach to method are discussed and illustrated using the analoev of a mathematical game. Scientific crcanomsni is shown to have a coating of scientific method, but to have systematically violated fundamental methodological principles. D arn in ’* method in contrast, had a comparative structure, and distinguished between common *nd discriminatory evidence. While there are methodological problems sn evolutionary biology, these are shown to be minor in comparison to that four*! in to c n o fk ciratxxiiun.