# Turing’s Biological Philosophy: Morphogenesis, Mechanisms and Organicism

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## Abstract

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## 1. Introduction

## 2. Turing’s Contribution to Biological Modelling

#### 2.1. Theoretical and Methodological Presuppositions

Unless we adopt vitalistic and teleological conceptions of living organisms, or make extensive use of the plea that there are important physical laws as yet undiscovered relating to the activities of organic molecules, we must envisage a living organism as a special kind of system to which the general laws of physics and chemistry apply.([30], p. 45)

#### 2.2. Turing’s Diffusion-Reaction Theory of Morphogenesis

## 3. Reconstructing Turing’s Choice

#### 3.1. Intellectual Biography and Influences

#### 3.2. Implicit Theoretical Factors

#### 3.3. Explicit Theoretical Reasons

One major result of the comparative morphological studies of the post-Darwinian period, and also of the contemporary period of renewed interest in morphogenesis, has been an appreciation of the fact that similar morphological and anatomical features may be found in organisms of quite distinct taxonomic affinity. These homoplastic developments, which have resulted from parallel or convergent evolution, have also been aptly described as constituting homologies of organisation and are of general occurrence in the Plant Kingdom. […] This being so, the factors which determine these kinds of pattern, or homologies of organisation, should be ascertained and closely investigated […] The contemporary explanation of comparable or homogenous developments in related organisms is that there are genes, or groups of genes, which are common to the organisms, and that these control or determine the observed developments**. But where similar features are present in unrelated organisms, the comparable developments cannot be attributed to common groups of genes. In attempting to explain the phenomenon of homology of organisation two possibilities may be entertained:

- (i)
comparable morphological features appear because essentially the same kind of process is operating in each of the non-related organisms; or- (ii)
that essentially different processes may, nevertheless, yield comparable morphological results.

On grounds of probability, the first explanation seems preferable to the second, but, because of the very great diversity of living organisms the second cannot, and should not, be eliminated out of hand. Whether we are concerned with developments which are considered to be more or less directly gene controlled, or with homologies of organisation, in which the importance of specific genetic factors has yet to be ascertained, the visible phenomena of morphogenesis have their inception in biochemical and biophysical reaction systems.([30], pp. 38–39)

Unless we adopt vitalistic and teleological conceptions of living organisms, or make extensive use of the plea that there are important physical laws as yet undiscovered relating to the activities of organic molecules, we must envisage a living organism as a special kind of system to which the general laws of physics and chemistry apply.([30], p. 45)

## 4. Discussion: The Limits of Mechanism and the Metaphysics of Life and Mind

Mechanists have tended to hold to some kind of reductionist strategy, that is, the belief that to understand higher level processes it is necessary to investigate them at lower levels of organization: for example, cells in terms of molecules, organs in terms of cells, organisms in terms of organ-system.([63], p. 266)

[The mechanistic programme] provided a way in which biology could dissociate itself from the earlier tradition of natural history that focused too much on descriptive methods and speculative theories such as reconstructing evolutionary histories of various taxa. True science […] looked not at hypothetical historical causes but at immediate proximate causes in terms of the material, knowable components of the process order [sic!] investigation. This was, of course, the model of true science exemplified by physics and chemistry.([63], p. 280)

Once Alan produced a fir cone from his pocket, on which the Fibonacci numbers could be traced rather clearly, but the same idea could also be taken to apply to the florets of the daisy flower. In this case it was rather harder to see how to count off the petals, and Joan wondered whether the numbers did not then arise merely as a consequence of the method of following them. This was pretty much the view of D’Arcy Thompson, who played down the idea that the numbers had any real significance in nature. They made a series of diagrams to test this hypothesis which did not satisfy Alan, who continued to think about ‘watching the daisies grow’.([6], pp. 261–262)

In consequence of the impossibility of finding a formal logic which wholly eliminates the necessity of using intuition, we naturally turn to ‘non-constructive’ systems of logic with which not all the steps in a proof are mechanical, some being intuitive.([67], p. 216)

## 5. Concluding Remarks

## Author Contributions

## Funding

## Conflicts of Interest

## Notes

1 | When using u and v as placeholders here, we are purposefully departing from Turing’s own notation because it is not consistent in his morphogenetic works. At the same instance, we follow his intuition not to distinguish between the substances and their concentration rates in notational terms. Since the concentration rates of the substances and the dynamics between them are what matters, a separate notation for the substances seems unnecessary from an ontological viewpoint. |

2 | A steady (stationary) state of a variable means that it does not change over time, whereas stability means that under conditions of minor perturbations, it will converge back to its initial steady state value. |

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**MDPI and ACS Style**

Greif, H.; Kubiak, A.; Stacewicz, P.
Turing’s Biological Philosophy: Morphogenesis, Mechanisms and Organicism. *Philosophies* **2023**, *8*, 8.
https://doi.org/10.3390/philosophies8010008

**AMA Style**

Greif H, Kubiak A, Stacewicz P.
Turing’s Biological Philosophy: Morphogenesis, Mechanisms and Organicism. *Philosophies*. 2023; 8(1):8.
https://doi.org/10.3390/philosophies8010008

**Chicago/Turabian Style**

Greif, Hajo, Adam Kubiak, and Paweł Stacewicz.
2023. "Turing’s Biological Philosophy: Morphogenesis, Mechanisms and Organicism" *Philosophies* 8, no. 1: 8.
https://doi.org/10.3390/philosophies8010008