The opposite of shirk is tawhid (monotheism), which means that there is no power in the universe except that of the Almighty God.
Tawhid has stages; they are:
1. Verbal admission or acceptance of tawhid; that is uttering that (laa ilaaha illallaah - there is no god but God) without believing in the sentence with the heart.
2. Believing with the heart when the above statement of monotheism is made with the tongue.
3. Realization of the unity of God through epiphany and numinous experience. In other words, one discovers that the vast multiplicity of creatures derive their existence from the One God, and recognizes that no power other than God's operates in the universe.
4. One sees nothing in the world except the Divine Being and perceives all creatures as emanations and reflections of that Being.
These stages of belief in tawhid guide us to recognize the cause of the disease of shirk. The root cause of shirk is immersion in the material world and forgetfulness in regard to God. In order to cure it, one must meditate upon the creation of the heavens and the earth and myriads of God's creatures. That may awaken within one the appreciation of the glory of God. The deeper his meditation and contemplation on the beauty of the universe and the mystery of its creation, the greater his faith in the existence and unity of God shall become.
The Quran says:
Such as remember Allah, standing, sitting, and reclining, and consider the creation of the heavens and the earth, (and say): `Our Lord, Thou hast not created this in vain. Glory be to Thee! sane us from the chastisement of the Fire. (3:191)
Imam al-Rida (A) has been quoted as saying:
Worship does not lie in copious prayer and fasting, but in the amount of contemplation in the works of God.
Muhammad Mahdi ibn abi Dharr al-Naraqi; Jami' al-Sa'adat