Fethullah Gülen’s answer to this question is short: Religion encompasses every aspect of life.
The foundation and the beginning of Islam are iman [faith] and iz’an [realization] the end of it is ihsan [acting and praying as if seeing God] and ihlas [honesty and sincerity from heart]. To believe in the truth of Uluhiya [Divinity] in such a way that not to recognize even the possibility of the opposite, and bond the heart with God; to undertake the responsibilities, to fulfill the obligations with a sensitivity as if seeing Him, or being in the presence of Him; and everything to be done around the axis of gaining His pleasure and nothing else. This is the concise expression of the truth of Islam.
Islam, the foundations of which are rooted in the messages of God and represented and practiced by the Prophet, is a divine religion from heavens. And those who make it as the life of his life are the believers and Muslims. The believers had defined this religion as the set of divine laws which orient people with their own free will and choice to goodness and kindness.
Islam is the last and the most perfect religion that God had chosen for humanity and honored with it. Because it is the last and the most perfect, it is, as it were, the elaboration and detailed explanation of the previous religions according to the needs of the modern age. But, the fact is that nowadays, this perfect system is going through an unfortunate time, for being represented by those representatives who are not qualified and by those who have no sense of fidelity to the original memory. Hence, despite its vastness, today it is imprisoned within the confines of narrowness and it is unable to express itself with its own language. This also means, at the same time, that all of the divine religions lack their proper true representatives to give proper expression these religions desire. First and foremost, Islam, by accepting all the messages of the previous Prophets, has come down by taking along their messages and with a view in mind that it would represent them according to the understanding of the contemporary age, in a sense it consists of the summary of them, it is the voice of all of them.
Islam may contain the meanings: the servant’s surrender to God, to obey his commandments, to march towards security by entering into a path of security, to promise safety to everything and everyone; being a person, no one feels unsafe or uncomfortable from his hands or tongue. For this reason, those who see it as consisting only of faith, as well as those who could not accept and internalize it through the ego would be counted among the mistaken. It is evident that both of the categories would be deprived of the spiritual or material, this worldly or otherwise of the rewards God promised. Nevertheless, it would be wrong to consider the “practice” as part of “faith” relying on these considerations. Those, who believe that the practice is religiously obligatory but fail to practice as demanded by the tenets, would be sinful, but still considered as believers. According to the Qur’an, the element sine qua non is “faith.” Islam is the sole path for it to become a depth of his nature, to become a second nature to human being. The practice without a faith is hypocrisy; despite the faith, not practicing it is a fisq [deviation from the truth] or hypocrisy. Since it is a secret, implicit unbelief, vices and immoral acts through the repentance, asking for forgiveness and again returning to God is always open to the possibility of forgiveness. Therefore, even if one does not do good deeds or practice the rituals, as long as one does not belittle them, or does not see them as insignificant, we should always think positively about him, and the judgment should not be passed as to his unbelief. At this point this should be pointed out, too, that the place where faith is born and develop is the heart and conscience, another important foundational component which God looks for in a faithful is: along with such a conscientious acceptance, doing good deeds and morality. Because of that, in either theoretical matters or the issues regarding the practice, as long as there is no coercion, the believer should stand by these matters that he or she has already accepted.
When that is the case, trying to present religion as if it was a matter of conscience only, is opposed to its spirit. The interpretation of iman and Islam according to the whims and wishes of the individuals would make it as a non-divine; it would make it mundane, a human affair. In actual fact, Islam is a divine tabligh, freeing humans from their whims and wishes, binding them to God and to the guidance of God. It takes as its addressee the ones who have reason and conscience; it would orient them to this worldly and other worldly good, with their own free will and choice, and promises eternal bliss to those who respond positively. Religion is a divine complement from the will of the divine to the partial human will.
According to Fethullah Gülen, there is a total Will which creates and rules the universe. This Will had given the human servant the ability to make choices and the possibility of freedom, of orienting his life towards knowledge and wisdom. To the extent that the human utilizes this possibility of choice closer to reason and morality, he meets with religion, the divine vision, and happiness.