The belief in the existence of God is inherent
Having ended the childhood and attained a discrimination between good and evil, if one consults his conscience, he will realize that he inherently loves virtues such as honesty, justness, and sympathy, that is, he appreciates the goodness of these traits and for this recognition he does not need any instruction or book, and if he is asked,
“How did you understand that honesty is a virtue?”
He would reply, “I did not learn this through reasoning but the recognition of its goodness is mingled with my conscience and nature.”
The belief in the existence of God (the Creator of the universe and its inhabitants) rests parallel to such inherent beliefs and to obtain this belief one does not need to be instructed or educated, but rather by consulting his nature and conscience, he will realize that this universe possesses an Omniscient and Omnipotent Creator.
Therefore, when we look back on the past history of mankind, we see that the belief in the existence of God has existed through all the previous eras even among people who lived in a savage manner and were not acquainted with culture and education. Of course, they occasionally erred in identifying God and assumed that sun or some stars or some earthly creatures are the creator of the universe but they never did without a principal belief in the existence of God.
Having clarified the meaning of an inherent belief in the existence of God, we should bear in mind one point:
At times, inherent things are neglected due to certain causes. Just as a light covered by a thick cloth which will stop illuminating, the God-knowing nature is occasionally covered by thick curtains of negligence, scientific conceit or over-indulgence in instinctive and impulsive desires. In this case, it is as if there were no such faith (in the existence of God) in one’s nature. But when these curtains are removed, one will automatically return to God.
Those who have deviated from the authentically innate belief in God as a result of wrongdoing and indulgence in instinctual desires will return to God and seek His help whenever they confront danger and feel that they can’t escape the threat by seeking ordinary means, for example, when they are faced with the threat of a plane crash or a car accident and so on. It demonstrates that at these moments, their God-knowing nature correctly manifests itself.
The sixth infallible Imām has concisely raised this point. Someone asked him to direct him toward the Creator of the universe (state reasons for His existence), the revered Imām replied thus,
“Have you ever been aboard a ship?”
“Has it ever happened that you have had a shipwreck and there was no other ship to rescue you and you didn’t know how to reach safety? (You could not rescue yourself through ordinary means).
“When you were desperately hopeless, did not you turn, deep in your soul, to one that would be able to save you?”
“Yes, I felt that there is a power which can save me.”
Imām al-Ṣadiq (‘a) observed, “The power toward whom you turned is God.”
This demonstrates that the power toward which the stricken people turn, intentionally or otherwise, and the same power to which one returns after removing the curtains of haughtiness, egoism, reliance on other people and dependence on superficial means, is the Creator of the universe who can fulfill needs and rescue the afflicted.
 Al-Tawḥīd by al-Ṣadūq, new print, p. 231.