A quotation by Imre Lakatos
That sometimes clear ... and sometimes vague stuff ... which is ... mathematics.
Quoted in P Davis and R Hersh The Mathematical Experience (Boston 1981).
The history of mathematics, lacking the guidance of philosophy, [is] blind, while the philosophy of mathematics, turning its back on the most intriguing phenomena in the history of mathematics, is empty.
Proofs and refutations (Cambridge, 1976).
Blind commitment to a theory is not an intellectual virtue: it is an intellectual crime.