  Despite philosophically significant differences in their views about the ultimate basis of the irreducibility of classical genetics, the image of biological knowledge that emerges from the antireductionists' writings is similar. The biological world consists of different domains of phenomena and each domain is best explained at a particular level of theoretical discourse. Hence, the ideal structure for biology is akin to a layer-cake, with tiers of theories, each of which provides the best possible account of its domain of phenomena. Biological sciences such as classical genetics that are couched in terms of higher levels of organization should persist, secure from the reductive grasp of molecular science, because their central theories (or patterns of reasoning) explain domains of phenomena that are best explained at levels higher than the molecular level. 