Hawzah News Agency (Qom, Iran) - Belief in the reality of God is a principle held in common by all heavenly religions: herein lies the decisive distinction between a religious person (no matter what religion is followed) and a materialist.
 

The Holy Quran asserts that the reality of God is a self-evident fact, one that does not stand in need of proof; doubt and obscurity on this question should not, as a rule, enter into this axiomatic principle. As the Quran says:
 

Can there be doubt concerning God, the Creator of the heavens and the
earth? (Sura Ibrahim, XIV: 10)
 

This dazzling self-evidence of divine reality notwithstanding, the Quran also opens up ways of removing contingent doubts from the minds of those who seek to arrive at belief in God by means of rational reflection and argument. To begin with, the individual normally has the sense of being connected to, and dependent upon, some entity that transcends the domain revealed by his own particular consciousness; this sense is as an echo of that call from the primordial human nature referred to earlier. It is this call that leads man to the source and origin of creation. The Quran says:
 

So set thy purpose for religion as a man by nature upright—the nature of
God (fitrat Allah) in which He hath created man.(Sura al-Rum, XXX:30)
 

It also says:
And when they board the ships they pray to God, making their faith pure,
for Him only; but when He bringeth them safe to land, behold! they ascribe
partners to Him. (Sura al-Ankabut, XXIX:65)
 

Man is continuously invited to study the natural world and meditate upon its marvels, all of which clearly point to the existence of God. These wondrous signs indicate and, in principle, prove the existence of a Being possessed of transcendent knowledge and supreme power, Who establishes and determines all things in harmony and perfection within the realm of existence:
 

Lo! In the creation of the heavens and the earth, and [in] the alternation
of night and day, are signs for men of understanding. (Sura Al Imran, III:190)
 

There are many other verses regarding this point, but we shall confine ourselves to this one alone as being altogether representative of the Quranic exhortation to meditate on the creation. It is clear that the ways of acquiring knowledge are not confined to what we have briefly alluded to; there are many ways of proving the existence of God, and these can be studied in detail in theological treatises.
 

Reference:

 Ayatollah Jafar Sobhani, Doctrines of Shii Islam, A Compendium of Imami Beliefs and Practices, Translated and Edited by Reza Shah-Kazemi, published by I.B.Tauris Publishers, london • new york  2003