If every momentary passion is to cloud a man's judgement and confuse his reason, if he is to become angry with every doctrine which he dislikes, if he is swept away by the emotional claims of mere prejudice when examining a theory or a viewpoint, if his heart is agitated with bitterness over personal injustices incurred to the extent that he declines to see both sides of a matter, he can never come to a right conclusion but will be tossed about like a rudderless ship--his emotions of hate, fear, or love forever interposing themselves between him and the truth. He who exhibits anger at views which he dislikes, for instance, is exhibiting his unfitness to study philosophy. For psychoanalysis of his state of mind yields the fact that he gets angry not because the views are untrue, but because they are repugnant to him, the individual named "X." We must learn to seek after truth not by our heartfelt emotions, nor by our vivid imagination, but by our keen reason.
-- Notebooks Category 6: Emotions and Ethics > Chapter 1: Uplift Character > # 515