It frequently happens that a man delivers his opinions with so much boldness and assurance, that he appears to be under no apprehension as to the possibility of his being in error.
 Immanuel Kant, Critique of Pure Reason (1791). copy citation

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Author Immanuel Kant
Source Critique of Pure Reason
Topic self-assurance error
Date 1791
Language English
Reference
Note Translated by J. M. D. Meiklejohn
Weblink http://www.gutenberg.org/files/4280/4280-h/4280-h.htm

Context

“Such a belief, contingent indeed, but still forming the ground of the actual use of means for the attainment of certain ends, I term Pragmatical belief. The usual test, whether that which any one maintains is merely his persuasion, or his subjective conviction at least, that is, his firm belief, is a bet. It frequently happens that a man delivers his opinions with so much boldness and assurance, that he appears to be under no apprehension as to the possibility of his being in error. The offer of a bet startles him, and makes him pause. Sometimes it turns out that his persuasion may be valued at a ducat, but not at ten. For he does not hesitate, perhaps, to venture a ducat, but if it is proposed to stake ten, he immediately becomes aware of the possibility of his being mistaken—a possibility which has hitherto escaped his observation.” source