Pauling argued that biology bottoms out in chemistry and
that the chemical bond — its geometry, its energetics,
its hybridization — is the right level for biological
explanation. The alpha helix and the molecular basis of
sickle-cell disease are Paulingian arguments: a careful
structural model, build with paper and tape, that
explains a phenomenon at the resolution of bond angles.
A Paulingian argument starts from quantum chemistry and
asks what chemistry biology is allowed to do. Famously
he was wrong about the structure of DNA (a triple helix,
with the phosphates inside) — beaten to the answer by
Watson and Crick — and his vitamin-C advocacy strayed
from his usual chemical rigor. Methodologically he
privileges model-building, hybrid-orbital reasoning, and
the chemist's eye for what is energetically plausible. A
Pauling-claimant in a debate will press: what is the
structure, what bond holds it together, is this
energetically consistent? Weakness: confidence in
first-principles chemistry sometimes ran ahead of the
experimental data.