Many working scientists applying for grants often tell me that the Haldane Principle has been an ideal that has become slightly eroded through the years.

BBC: How to divide up the 'science cake'?

Another critically important principle when considering the ideal tax rate is something called "Hauser's Law, " named after investment economist Kurt Hauser, which shows that over the last six decades tax revenue as a percent of GDP has been about 19%, regardless of fluctuations in tax rates.

CNN: Why America needs a tax reformation

The budget that Orszag and his colleagues drafted was the Platonic ideal of Obamaism, a Presidential statement of principle.

NEWYORKER: Money Talks

After two terms as governor, Reagan had matured into what Buckley considered a nearly ideal conservative politician: a shrewd leader as well as a man of principle.

NEWYORKER: Confounding Fathers