Donaldson's idea of using global analysis to get more insight about the topology of manifolds. Nowadays it is clear to us that (non-linear) modlui spaces give something new, and more than linear (abelian) Hodge theory, for example, but I think at that time this was really new.

Donaldson's idea of using global analysis to get more insight about the topology of manifolds. Nowadays it is clear to us that (non-linear) moduli spaces give something new, and more than linear (abelian) Hodge theory, for example, but I think at that time this was really new.