sentences:  While Hennig insisted that different classification schemes were useful for different purposes, he gave primacy to his own, claiming that the categories of his system had "individuality and reality" in contrast to the "timeless abstractions" of morphology-based classifications.Formal classifications based on cladistic reasoning are said to emphasize ancestry at the expense of descriptive characteristics.Nonetheless, most taxonomists today avoid paraphyletic groups whenever they think it is possible within Linnaean taxonomy; polyphyletic taxa have long fallen out of fashion.