A delusion is an erroneous judgment regarding the condition of affairs, the end to be attained, the motives to be followed, or the means to be employed in practical life. Faith teaches that the human mind has been darkened by original sin. Unless a person be very humble and circumspect, therefore, his perceptions will easily be blurred, his judgments erroneous, and the dictates of his reason reprehensible.
In consequence of delusions individuals mistake in themselves (1) the desire of virtue for virtue itself, (2) confuse passion with virtue, (3) and invariably overestimate their own ability and productions while underrating the ability and deeds of others. In consequence of this same delusion man often (1) neglects to give God His due (2) and even disregards the proximate occasion of sin, as though he were already confirmed in virtue.
Two causes combine to give permanence to in the human mind. The first is mental pride, which is apt to dispense with salutary reflection on the tendency of human nature and on the operation of grace, and, by mistaking imagination for divine inspiration, cause ''fools to rush in where angels fear to tread." The second cause of delusions is an unbridled self-love. This may blind a person to that extreme that he cannot see '' the beam in his own eye, though he sees the mote in his neighbor's eye" (Matt, vii. 3).