On Being the Right Size


"On Being the Right Size" is a 1926 essay by J. B. S. Haldane which discusses proportions in the animal world and the essential link between the size of an animal and these systems an animal has for life.
It was published as one of Haldane's collected essays in Possible Worlds and Other Essays.

Thesis

Haldane's thesis is that sheer size very often defines what bodily equipment an animal must have:
Many of his examples are based on the square-cube law, although he does not use that terminology.
The bigger an animal gets, the more it would have to change its physical shape, but the weaker it would become.

Influence

This link became known to others as Haldane's principle, being referred to as such by urban planning theorist Jane Jacobs.
Another planning theorist, Christopher Alexander, refers to this principle in his theory of Independent Regions in A Pattern Language, citing Haldane:
The conceptual metaphor to animal body complexity has been of use in energy economics and secession ideas.