256 important contributions to this topic by contemporary biologists (Roth 2008). Biology was even of great importance for the general architecture of Kant’s philoso- phy reflected in his three Critiques. While the Newtonian laws were the prime example for a science in his first Critique, the Critique of Pure Reason (1781, 1787), biology represented a central topic in his third critique, the Critique of Judgment (1790). Here, Kant developed a theory of the organism, which would become influential for the life sciences of the nineteenth century. This theory makes a strong claim about the way we analyse organisms as opposed to other objects of nature. Organisms, Kant believes, are not fully accessible for us through mechanistic explanations on the basis of general laws exemplified by Newton’s principles. In a famous passage, he says: ‘…it would be absurd for humans even… to hope that there may yet arise a Newton who would make comprehensible even the generation of a blade of grass according to natural laws…’ (Kant 1900ff Vol 5, 400). One may well rephrase this sentence by saying human beings are not able to mathematise biology. In spite of such a strong proposition, Kant supports mechanistic studies of organisms because ‘…without this no insight into the nature of things can be attained’ (Kant 1900ff Vol 5, 410). Thus, Kant’s attitude appears to be almost schizophrenic. On the one hand, he posits that organisms will always resist complete mechanistic and, in particular, mathematical explanations. The reason is that they have a certain goal- directedness (purposiveness), which humans can describe only in functional terms, i.e. in the same way as we describe a machine. He calls the type of judgment we use in analysing organisms and artefacts teleological judgement. On the other hand, biology as a science requires, according to Kant, a mechanistic approach using forward causal explanations, which ultimately need to be expressed in mathematical terms. Kant repeatedly stresses the point that the necessity of this dual approach for studying organisms is not a property of nature itself, but rather due to our limited faculties. He explicitly criticises all vitalistic approaches which ask for special laws of living matter. Kant’s third Critique was widely read by scientists in the nineteenth century and apparently had a significant impact on the research agenda of biologists. It freed the working biologist from the burden to explain every aspect of organisms on the scarce basis of the mechanical laws of the early nineteenth century—chemistry was still in its infancy—but at the same time motivated experimental approaches aiming for causal explanations. This attitude was termed teleomechanism (Lenoir 1989) because it combined mechanistic analyses with the idea of a given machine-like (purposive) structure that itself required no further theoretical grounding in known natural laws. We can still see this attitude at the end of the nineteenth century Dev Genes Evol (2011) 221:255–279 in the work of Hans Driesch, who wrote: ‘On the basis of this given structure, this machine, we gain a causal understanding of the functions with the help of chemistry and physics…. But the given structure of the living can only be understood in teleological terms’ (Driesch 1894). This passage is from Driesch’s Analytical theory of development, one of the great and influential books in the history of developmental biology. Inspired by ideas of Wilhelm Roux who had coined the term Entwicklungsme- chanik, Driesch started his research with the goal to explain development on the basis of physics and mathematics. But soon, his experiments with sea urchins brought him into opposition to Roux who was a follower of Weismann’s Keimplasmtheorie which held that differentiation in devel- opment results from the specific partitioning of the genetic material. Driesch, on the other hand, correctly assumed that the complete genetic material was present in each cell nucleus. ‘Insofar as it contains a nucleus, every cell, during development, carries the totality of all primordia…’ (Driesch 1894). This conclusion was in part based on Driesch’s observation of self-regulation and scaling during development. When he separated the blastomeres of two- cell sea urchin embryos, each isolated blastomere gave rise to a complete embryo which was only smaller in size compared to a normal one. The experiments worked also with four-cell and partially with eight-cell embryos. How could it happen that a part of an embryo reconstituted the whole structure with all its elements correctly arranged, but just on a smaller scale? To explain the scaling behaviour, Driesch described the sea urchin embryo as a ‘harmonious equipotential system’. The potential of a given cell to differentiate into a particular part of the body depends on its position within the embryo. Thus, Driesch introduced the concept of ‘positional information’ 75 years before it was re-introduced and refined by Lewis Wolpert (Wolpert 1969). Although Driesch first sought physical explanations for the ‘harmonious equipotential system’, further experi- mental studies convinced him that the phenomena of scaling and self-regulation could not be explained by the laws of physics and chemistry known at his time (Driesch 1899). Embryonic development seemed to require a form of self-organisation, which had not been observed in inani- mate nature. Driesch postulated additional laws restricted to organismic life, and thus became one of the last famous vitalists in the history of biology. Now, he also explicitly broke with Kant’s more cautious attitude. In Kant und das Ganze, Driesch states that Kant’s use of teleological principles as mere methodological tools for analysing organisms was inconsistent and that Kant, on the basis of his own theory, should have adopted a vitalistic stance (Driesch 1924). Driesch was harshly criticised by his colleagues, in particular by Wilhelm Roux in his reply The self-regulation,