The transition from the transcendent to the immanent view can be traced in each aspect of the life problem. . . . We now turn to the transformation of the theory that is to explain the species characteristics of a life-form and their constancy through the generations.
The pure typical case of a transcendent explanation is Linnaeus' theory, according to which God created at the beginning of the world the various animal species and endowed the individuals of each species with the ability to bring forth their own kind; in fact, the species was the quintessence of the individuals who have descended from each other through procreation; in theory the species was coined by God's creative hand. When fixity of the species was understood in this way, there was hardly any reason to look for the inner causes of the individual's character; the reference to God as the transcendent creator of the world in its thusness was sufficient.
Of all the theoreticians of biology of his day, Linnaeus was most deeply immersed in the Christian worldview. Linnaeus believed that the world actually had a definite beginning; there was a day and an hour when the world, in the organization of its existence, emerged from the chaos through God's creating hand. When this belief died, the teaching of the species and its duration became questionable, leading to those transformations in the theory with which we must now concern ourselves.
When the world was no longer believed to be the creation of a higher being, the act of creation was no longer the real starting point in time of the world and its many species. The "world" was no longer a finite event that was on some level actually delimited in time by a transcendent being. And while the similarity of individuals had been understood as caused by a similar pressure of the divine hand, the theory of the fixity of the species was now also shaken. The succession of generations no longer had a finite beginning in the creation or an origin of its specific laws; instead, the succession could be traced from any individual back into infinity without this regression coming up against a point of origin for the law of the species.
The result was a peculiar, undecided state. The concept of creation was replaced by the idea of infinity. Preformist theory, which envisioned the germs of all individuals contained in the first progenitors of each species—for example, the human ones in the body of Eve—had to change, and replace this real definite beginning with the series of infinite encapsulations.
Now if the image of the created finite succession of generations is supplanted by the idea of an infinite succession without any real beginning, the idea that the law of this succession was created transcendentally at the beginning of the succession of generations becomes meaningless, and speculation forces us moreover to the formulation of that law in such a way that the law of the species can be directly discerned in each individual of the species.
A shift of the cause of the fixity of the species to infinitely distant specimens became pointless because according to the law of the infinite succession it must be assumed that each individual was descended from a predecessor. This led to the speculative leap to the lawfulness of the species as a real cause [Realgrund] that is at work in all individuals of a species, thus necessarily also in the one currently under observation, without having to be traced back to preceding ones.
This finitization of the law of the species in turn invalidates the idea of infinity that, for one speculative moment, served as the explanatory cause of the species—that is, for the moment when the act of creation had ceased to be the starting point of the succession of generations and it was still believed, in accord with the rationalistic encapsulation theory, that the regression to the preceding individual could explain the one descended from it. This open, undecided moment came to an end with the abolition of the idea of infinity and with the adaptation of the concept of law to the finite style of the new concept of the organism. . . .