In a recent article in Philosophy of Science Janet Travis [13] seeks to refute the argument for evolutionary progressivism which is based on a series of dominant life forms on the grounds that there is no rigorous definition of that concept. In particular she claims that the definitions formulated by Sir Julian Huxley and George Gaylord Simpson fail adequately to exclude any group of organisms. The concept of dominance is therefore alleged to be meaningless and the argument for progress invalid.