The classification of finite simple groups is very interesting for a couple of reasons at least. The formulation required the list of sporadic groups to be complete; and the empirical approach of the discoverers of sporadic groups was important to the acceptance that the list was right. I remember the champagne for J4 ...

@Gerry Myerson An early example is Jacobi saying that Dirichlet is the only really rigorous mathematician around; and juxtaposing that with his use of Fourier series in prime number theory (books.google.co.uk/books?id=tqaWlHIsZXAC&pg=PA29). By the time you have G. H. Hardy commenting on Ramanujan and the complex zeroes of the Riemann zeta function, I believe the thought had become a commonplace.

@jeq books.google.co.uk/… explains something about a famous example, and Severi's general shamelessness.

@Jon Well, maybe - thanks for pointing that out. The policy on external links should probably be applied at some later time.

It's more complicated than that (Dynin wasn't the first to add something about the paper). But I have moved two paras off the page and onto the talk page so that they can be discussed.