Man is a worshipping creature. He was created by God to worship his Creator. To worship does not mean merely to engage in “religious” rituals or say prayers; it means to serve in the whole of one’s life. Man was not created for himself but for a purpose beyond himself, namely to serve God, and he can only find true purpose and ultimate meaning in life when he seeks to live his life in the service of God. Mankind is hard-wired to this purpose. Man always looks for meaning and purpose in life, and he can only truly find this purpose outside of himself in the service of the God who created him. As Augustine of Hippo said “Thou [O Lord] has formed [i.e. created] us for Thyself, and our hearts are restless till they find rest in Thee” (Confessions, I.1).
When a man turns away from God and says he does not believe in God, his nature does not change. The non-believer still finds the ultimate meaning and purpose of life in worshipping, i.e. serving. But he now serves something else, someone or something other than the God he was created to serve. The Bible calls this idolatry, i.e. the putting of someone or something else in the place of God. Men look to these idols for the purpose and meaning of life instead of looking to God for the purpose and meaning of their lives, which is what they were meant to do.
It is important to understand at this point that the term religion does not necessarily imply belief in a supernatural personal God, such as the God of Christianity, Judaism, or Islam. The word religion does not mean theism. Theism (from the Greek word for God, theos) refers to belief in the existence gods or god, and especially to a God who is supernaturally revealed to man and who sustains a personal relationship to him (The Concise Oxford Dictionary of Current English, Eighth Edition. 1990). Theism is therefore a form of religion. All theistic faiths are religions. But not all religions are theistic. Religion refers to the belief system or world-view that structures human thought, life and society. The word religion comes from the Latin word religio, which means obligation, bond, reverence for the gods, from the verb religare, meaning to bind. Inevitably, religion brings obligation, duty, i.e. life in accordance with an obligation that binds man. The root of religio is lig, to bind, and is cognate with the Latin word lex, meaning law (Lewis and Short, A Latin Dictionary [Clarendon Press, 1879]). Religion, therefore, is what binds man, what structures his life; and it structures the life both of the individual and society. Christianity, Judaism and Islam are clearly religions that structure human thought, life and society. They are also theistic religions. Secular humanism is also a belief system or world-view that structures human thought, life and society; it is, therefore, a religion, but it is not theistic.
Of course it is secular humanism that is now the dominant religion in Western society, and there are many different versions, or denominations, of this secular religion, just as there are many different denominations in the Christian Church. Although the religious nature of secular humanist beliefs is not acknowledged by many people some secular humanists do recognise that secular humanism is a religion. For example the preamble to the Communist Manifesto speaks of “religious humanism.” The United States Supreme Court has also defined secular humanism as a religion, stating that “Among religions in this country which do not teach what would generally be considered a belief in the existence of God are Buddhism, Taoism, Ethical Culture, Secular Humanism and others” (Torcaso v. Watkins, 367 U.S. 488  footnote 11).
When men reject God as their Creator and the one who provides ultimate purpose and meaning for their lives, they look elsewhere for purpose and meaning in life. Whatever or whomever they look to in order to find meaning and purpose in life takes the place of God, who alone is the one to whom they should look for the meaning and purpose of life. Whatever takes the place of God in one’s life in this way is an idol. These idols may be God equivalents such as supernatural beings, or institutions such as the State, or ideologies, such as evolution and socialism. Or men may look to their own lives and seek the ultimate meaning and purpose of life in the pursuit of their own happiness and fulfilment. Nevertheless, when something takes the rightful place of God in our life it becomes an idol. These things are not necessarily wrong in themselves, but the purpose that they are made to serve when they are believed to provide ultimate meaning for man’s life is idolatrous because they take the place God.
All sorts of things can serve as idols. Idols are not just the pagan gods and goddesses, therefore, but anything that takes the place of God in our lives. For example, people look to the great and the famous, to the State and the party, to their hobbies or their bank balance, even to their annual holidays, anything other than the God of the Bible, and there they seek ultimate meaning and significance for their lives. But of course these things cannot provide what they are looking for. All these things ultimately disappoint, since they cannot fill the place of God in man’s life. Idols always fail, and ultimately they crush the spirits of men because idols are tyrants that cannot deliver in terms of fulfilling man’s ultimate purpose in life—to serve God.
There are so many different religions because men put so many different things in the place of God. In fact any aspect of the created order can become an idol, whether physical, ideological or intellectual. Even the Christian Church can become an idol that men put before God. One of the greatest of English theologians, the seventeenth-century Puritan divine John Owen, complained in his day that “The secular, worldly interest of multitudes lying in this presumptive church and the state of it, they preferred and exalted it above all that is called God, and made the greatest idol of it that ever was in the world; for it was the faith and profession of it, that its authority over the souls and consciences of men is above the authority of Scripture” (Works Vol. XV [Goolde edition], p. 224f.).
The answer to the question therefore is that there are so many different religions because men choose so many different things to worship in the place of God; they build up different ideologies and beliefs that provide them with an overarching structure and meaning to life, a world-view, in term of which they seek to find meaning and purpose for their lives. Ultimately, therefore, there are only two kinds of religion, the true religion, and false religion, i.e. idolatry, but idolatry leads to as many different sorts of religion as men choose different things in terms of which to seek meaning and purpose for their lives.
Man is a worshipping creature. He will worship someone or something because he was created to do so. He can no more deny the reality of this than he can deny himself the air that he breathes. He can deny it in mere words for sure; but he cannot deny the reality of this in his actions, in the way that he lives. It is never the case that man chooses not to worship. And by worship I do not mean merely words and symbols, i.e. religious rites and ceremonies. Worship is far more than that. Worship is the dedication of one’s life in service to the object worshipped. And such worship is inescapable for mankind. Man worships with every breath that he takes. The question is, “Whom or what, and how, does he worship?” We can pervert the meaning of the worship we offer by offering it incorrectly or by offering it to the wrong object. In fact, this is the whole of man’s condition outside of Christ. The non-believer worships his gods daily no less than the believer, but the gods he worships are false gods, idols. He does not give the God of the Bible the worship that rightfully belongs to him and to him alone. Instead he worship some other object or objects and ascribes all the attributes of deity to these objects, which are mere creatures, i.e. aspects of the created order, whether a block of wood, or stone, a demon, or an ideology of his own making. This is why there are so many different religions.
Answered by Stephen Perks