Chapter XXXIX: Section 39: If you want your judgment to be accepted, express it

coolly and without passion. All violence has its seat in the _will_; and so, if your judgment is expressed with vehemence, people will consider it an effort of will, and not the outcome of knowledge, which is in its nature cold and unimpassioned. Since the will is the primary and radical element in human nature, and _intellect_ merely supervenes as something secondary, people are more likely to believe that the opinion you express with so much vehemence is due to the excited state of your will, rather than that the excitement of the will comes only from the ardent nature of your opinion.