Haldane was the third of the modern-synthesis founders
(with Fisher and Wright) and the most willing to think in
vivid biological pictures. "On Being the Right Size" — the
essay where he argued that scaling laws constrain animal
form — is the prototype of a Haldanean argument: take a
first-principles physical or mathematical constraint and
ask what biology must look like to obey it. He estimated
mutation rates, selection coefficients, and the cost of
natural selection in tractable closed forms; he flirted
with kin selection decades before Hamilton ("two brothers
or eight cousins"). Methodologically he is a back-of-the-
envelope scientist — a Haldane-claimant in a debate will
reach for a Fermi-style estimate before any detailed
model. He is comfortable arguing across scales, from
enzyme kinetics to phylogeny. Weakness: his Marxist
politics sometimes colored his biology, and his
contributions are scattered across many small papers
rather than consolidated. A Haldanean argues that biology
submits to physics, math, and a willingness to do the
arithmetic on the back of a napkin.