name that philosopher
"Every method of inquiry is justified; disputes can only arise over the question of the purpose and fruitfulness of a given method."
* * * * * *
If you guessed the epistemological anarchist Paul Feyerabend, you're wrong. It's Carnap, in 1932's "Psychology in Physical Language" (p. 192 in the Ayer collection). (On this blog, 'Carnap' is always a pretty good guess.) It sounds to me like his Principle of Tolerance, with methods of inquiry substituted for logical systems.