Quote attributed to H. L. Mencken and found in fortune databases everywhere.
While originally applied to more hard and fast disciplines such as the hard sciences and mathematics, it strikes me as a concise formulation for what some social scientists call divergent problems: complex socio-economic and political quagmires that cannot be resolved within a single presidential term, or even a few decades for that matter.
A few examples: sexism, racism, poverty, environmental law, right to life v. freedom of choice, the safety net v. the cycle of poverty, whether to reform language to make it more politically correct or stop reading sociology into grammar, and What the hell should we do about MicroSoft?