  Even induction from sense experience is not of one type. It may start with evidence taken from different levels of perceptual and experiential complexity and is at work at different stages of an investigation. This approach to induction is guided by the character of scientific knowledge itself, which Wright understood to be the relating of particular facts to more general ones (PD 205–206). But it also follows the character of natural phenomena. In biology in particular, the new science of evolution concerns the “external economy of life” and thus must investigate an accumulation of related facts of observation at the level of secondary causes (PD 99–100). Induction may come from ordinary experience, experiment, or the inspections of the field naturalist. He said, “Inductions are still performed for the most part unconsciously and unsystematically…. But when and however ideas are developed science cares nothing, for it is only by subsequent tests of sensible experience that ideas are admitted into the pandects of science” (PD 47).