Charles Sanders Peirce (1839-1914), Reasoning and the Logic of Things: The Cambridge Conferences Lectures of 189
8 (Cambridge: Harvard University Press, 1992), p. 178 (note omitted):
Upon this first, and in one sense this
sole, rule of reason, that in order to
learn you must desire to learn, and
in so desiring not be
satisfied with what you already
incline to think, there follows one
corollary, which itself deserves to be
inscribed upon every wall
of the city of philosophy.
Do not block the way of inquiry.