The pattern that connects (Bateson) is also the pattern that creates, the sign that determines the form of existing things or systems. We discover these patterns by observing that similar beings have similar origins.
All natural classification is then essentially, we may almost say, an attempt to find out the true genesis of the objects classified. But by genesis must be understood, not the efficient action which produces the whole by producing the parts, but the final action which produces the parts because they are needed to make the whole. Genesis is production from ideas. It may be difficult to understand how this is true in the biological world, though there is proof enough that it is so. But in regard to science it is a proposition easily enough intelligible. A science is defined by its problem; and its problem is clearly formulated on the basis of abstracter science.
— Peirce, CP 1.227 (1902)
In biology, the genetic ‘idea’ is more recently called the genotype, and we now have a better understanding of its role in producing organisms classified by phenotype. But many biologists still do not see these as types in the Peircean sense, which here he calls ‘ideas’:
All classification, whether artificial or natural, is the arrangement of objects according to ideas. A natural classification is the arrangement of them according to those ideas from which their existence results. No greater merit can a taxonomist have than that of having his eyes open to the ideas in nature; no more deplorable blindness can afflict him than that of not seeing that there are ideas in nature which determine the existence of objects.
— Peirce, CP 1.231 (1902)