I criticize the particular argument for evolutionary progressivism which is based on the concept of a series of "dominant life forms." My procedure is to show that there is no rigorous definition for the concept of "dominant life form." I examine several attempts to define this concept by Julian Huxley and a new formulation of the concept by G. G. Simpson and show that none of the criteria either of these men develop for determining which groups of organisms can be (...) classified as dominant are adequate to exclude any groups of organisms from the classification. The concept proves so broad as to be meaningless. Since it is a key concept in the particular argument for progressivism that I discuss, the criticism of the concept demonstrates the argument to be invalid. (shrink)