"There are four causes of infidelity and loss of belief in Allah: hankering after whims, a passion to dispute every argument, deviation from truth; and dissension, because whoever hankers after whims does not incline towards truth; whoever keeps on disputing every argument on account of his ignorance, will always remain blind to truth, whoever deviates from truth because of ignorance, will always take good for evil and evil for good and he will always remain intoxicated with misguidance. And whoever makes a breach (with Allah and His Messenger) his path becomes difficult, his affairs will become complicated and his way to salvation will be uncertain.Source: http://www.al-islam.org/masoom/sayings/saying5.html
Similarly, doubt has also four aspects absurd reason- ing; fear; vacillation and hesitation; and unreasonable surrender to infidelity, because one who has accustomed himself to unreasonable and absurd discussions will never see the Light of Truth and will always live in the darkness of ignorance. One who is afraid to face facts (of life, death and the life after death) will always turn away from ultimate reality, one who allows doubts and uncertainties to vacillate him will always be under the control of Satan and one who surrenders himself to infidelity accepts damnation in both the worlds."
Hazrat Ali (A.S)