‘Shirk’, the word used for idolatry in Arabic means “partnership/association”.

In the Qur’an, to practise idolatry is to associate any other being, any other person, or concept with Allah, considering them to be equal to Allah, and to act upon this unsound belief.

In translations of the Qur’an, idolatry is explained as “associating a partner with Allah”. It is expressed thus: “having another god besides Allah”, or “worshipping another god besides Allah”.

In its broadest sense, idolatry is to adhere to principles and values, or pursue a life style other than is consistent with the teachings and moral values of the Qur’an. Someone adopting such principles simply sets up the person laying down these principles as a partner to Allah. This person may be anyone; his father, grandfather, an ancestor he may so exalt the society he is a member of, the founders of an ideology, a philosophy or its followers. In this broad sense of idolatry, someone adhering to a different way of living other than the Qur’an, simply practises idolatry. He may call himself an atheist, Christian, or Jew. He may even appear to be a Muslim, performing his regular prayers, fasting and obeying the laws of Islam. Nevertheless, anyone harboring a thought or judgment opposing the Qur’an is a mere idolater; by such a stance he simply manifests his acceptance of the existence of a ruler other than Allah.

Idolatry does not essentially require an absolute denial of the existence of Allah. Rather, the majority of the idolaters avoid explicitly accepting such an attribute or “title”. Never scrupulous in conduct, they deceive themselves throughout their lives. On the Day of Judgment, they still reject being involved in idolatry. The stance they adopt is explained in the following verse:

One day shall We gather them all together: We shall say to those who ascribed partners (to Us):

“Where are the partners whom you (invented and) talked about?” There will then be (left) no subterfuge for them but to say: “By Allah, our Lord, we were not those who associated other gods with Allah.” Behold! How they lie against their own souls! But the  (lie) which they invented will leave them in the lurch. (Al-Ana‘am, 22-24)

An idolater does not necessarily have to make “declarations”. You will certainly never hear a statement like this: “I hereby take this divine being as a god besides Allah and I swear an oath of loyalty to him.” Idolatry resides primarily, in the heart and is then disclosed through word and deed. From the standpoint of the Qur’an, having a preference for a being other than Allah underlies it. Giving preference to the will of some person over the Will of Allah, for instance, fear of other people rather than fear of Allah, or an attachment to some person rather than to Him are examples of idolatry described in the Qur’an.

From the foregoing, it is clear that idolatry is the diversion of the feeling of “love” from Allah to other beings. The strong attachment formed to idols is explained in the following verse:

Yet there are men who take (for worship) others besides Allah, as equal (with Allah): They love them as they should love Allah. But those of the Faith are overflowing in their love for Allah. If only the unrighteous could see, behold, they would see the penalty: that to Allah belongs all power, and Allah will sternly enforce the penalty. (Surah Al-Baqara, 2:165)

This verse makes it clear that “love” given to the wrong people lays the basis for “worshipping others than Allah” as well as idolatry. Unlike believers, unbelievers can never maintain an intimate relation with their Creator. They love either themselves or others, or both; they share out their love among their fathers, sons, brothers, wives, husbands, lovers, the people they are surrounded by, and so on. As well as for people, unbelievers feel attachment for non-living things, or rather concepts like money, possessions, houses, cars, status, prestige, etc.

The superior and gorgeous properties of all living things and non-living things alike, are mere reflections of the infinite attributes of Allah. The unique possessor of these features is Allah and therefore the only One worthy of loyalty, devotion and love. Feeling an attachment then for anything other than Allah is mere association of partners with Allah.

In another verse, in the words of Prophet Abraham, it is asserted that unbelievers leave Allah and strengthen the bond with their idols:

And he said: “You have taken (for worship) idols besides Allah, out of mutual love and regard between yourselves in this life; but on the Day of Judgment you shall disown and curse each other: and your abode will be the Fire, and you shall have none to help you.”(Al-Ankaboot, 25)

Passion for women is the most striking example of ascribing partners to Allah in terms of love. The woman in question can be anyone—a spouse, a girl friend, or even a woman to whom one is platonically attracted. In consequence, if the love felt for a woman makes a man drift apart from Allah, makes him see a woman as equal to or at a higher level than Allah, then this is explicitly “ascribing partners to Allah.” Such a mentality, assumed to be innocent behaviour in society, has serious consequences, however, in the presence of Allah:

(The Pagans), leaving Him, call but upon female deities: they call but upon Satan the persistent rebel! (An-Nisa, 117)

This point of view also holds true for women. This type of love, unacceptable in the presence of Allah, is however encouraged in modern societies under the “innocent” rubrics of “love”, “romanticism” or “dating.” The indoctrination of romanticism- especially targeting young people—has devastating effects upon new generations. This is surely a great hindrance to the healthy development of the youthful mind and consciousness. As a result of this indoctrination, generations devoid of understanding, come into being. In such circumstances, the members of society live in a total unawareness of the purpose of their existence on Earth, and the exigencies of their religion and faith. Such people simply cling to an ignorant way of living and lead their lives without knowing what love of Allah or fear of Allah really means.

Another reason for the individual to drift into shirk is fear. Just like love, fear should be felt only for Allah. One who feels or shows fear for created beings simply attributes individual might to them. This is idolatry, pure and simple.
Allah has said:

“Take not (for worship) two gods: for He is just One Allah: then fear Me (and Me alone).” To Him belongs whatever is in the heavens and on earth, and to Him is duty due always: then will you fear other than Allah? (An-Nahl, 51-52)

Unbelievers go in great fear of other people. This is narrated in the Qur’an:

...When (at length) the order for fighting was issued to them, behold! A section of them feared men as - or even more than - they should have feared Allah. They said: “Our Lord! Why have you ordered us to fight? Could you not grant us a brief respite?”...(An-Nisa, 77)

Apart from the feelings of love and fear, there are other attitudes leading man to idolatry.

The basis of idolatry is the preference for a person, or a thing over Allah, for instance, to prefer somebody’s approval to Allah’s, to fear somebody as one fears Allah or to love him as one loves Allah…Or to do for an idol what he doesn’t do for Allah, or to make a sacrifice which he does not do for Allah’s approval.

Given the foregoing arguments, it would be a shallow interpretation indeed to define idolatry as the worship of statues. This is surely an argument used by unbelievers to justify their stance. According to their explanation, idolatry ceased when the idols in the Ka’ba were broken at the time the message of Islam was communicated. If this argument were true, then the hundreds of verses warning believers against idolatry, and providing a detailed explanation about it, would have relevance only to a few primitive tribes in our day—a piece of a reasoning quite contradictory to the essence of the Qur’an. Furthermore from the Qur’an which will prevail until the Day of Judgement we understand that, in every age, pagans lived together side by side with believers. The related verses follow:

Strongest among men in enmity to the believers you will find the Jews and Pagans... (Al-Maeda, 82)

Turn back in repentance to Allah, and fear Him: establish regular prayers, and do not be among those who associate other gods with Allah Turn to Him, be careful of your duty to Him, be steadfast in prayer and do not be of the polytheists, who split up their religion, and become (mere) sects, each party rejoicing in its own beliefs! (Ar-Rum, 31-32)

As the verses suggest, one of the most significant characteristics of polytheistic societies is their approach to true religion; they reject some commandments of the religion revealed by Allah and hence form divisions within the religion. The members of these divisions assume themselves to be on the right path and fight with one another. However, it should be kept in mind that even a minor diversion from the Qur’an is an addition or alteration to what Allah has revealed, and consequently a source of polytheism.

In the verses below it is stated that no deed of the pagans is accepted by Allah; even their prayers and worship:

But it has already been revealed to you, as it was to those who went before you, “If you were to associate other gods with Allah, truly fruitless would your work in life be,” and you would surely be in the ranks of those who lose all spiritual good”. (Az-Zumar, 65)

Out of what Allah has produced in abundance in tilth and in cattle, they assigned Him a share: they say, according to their fancies: “This is for Allah, and this for our partners!” But the share of their “partners” does not reach Allah, whilst the share of Allah reaches their “partners” ! Evil and unjust is their judgement! (Al-Anaam, 136)

A believer may commit various sins. However, behind these sins, there is no question of a revolt or a similar intention or act against Allah. What makes idolatry different from other sins is that, in contrast to the other sins, idolatry assigns another god besides Allah and invents a lie against Him. Thus idolatry is the greatest sin. It is in a way a manifestation of disrespect to Allah.
Accordingly, Allah mentions in the Qur’an that He will forgive any sin except idolatry:

Allah does not forgive those who set up partners with Him; but He forgives whom He pleases; for anything else; to set up partners with Allah is to devise a sin most heinous indeed. (An-Nisa, 48)

Allah does not forgive the sin of associating other gods with Him; but He forgives whom He pleases for sins other than this: one who associates other gods with Allah, has strayed far, far away (from the right). (An-Nisa, 116)

Therefore in many verses of the Qur’an, Allah warns believers against idolatry and deters them from this greatest sin. The Qur’an explains idolatry in detail:

O you who believe! Truly, the Pagans are unclean... (At-Tawba, 28)

Being true in faith to Allah, and never assigning partners to Him: if anyone assigns partners to Allah, it is as if he had fallen from heaven and been snatched up by birds, or the wind had swooped (like a bird on its prey) and carried him off to far-distant place.
(Al-Hajj, 31)

Turn back in repentance to Allah, and fear Him: establish regular prayers, and do not be among those who associate other gods with Allah. (Ar- Rum, 30)

Behold, Luqman said to his son by way of instruction: “O my son! Serve no other deity besides Allah: for false worship is indeed the greatest wrong-doing.” (Luqman, 13)

Say: “I am but a man like yourselves, (but) the inspiration has come to me, that your Allah is one Allah: whoever expects to meet his Lord, let him do what is right, and, in the worship of his Lord, admit no one as partner.” (Al-Kahf, 110)

Anything, living or non-living, which the pagans assign as partners to Allah by no means  possess any divine attributes.

Allah states in the Qur’an that these partners can neither harm them nor profit them (Jonah, 18), cannot create anything (Jonah, 34, Al-Araf, 191), they cannot help anyone, not even themselves (Al-Araf, 192), and cannot lead to the righteous way (Jonah, 35). Despite their all being inherently weak, these “partners with Allah” are set up by pagans. The main reason for such an attitude is the fact that Allah bestows some of His attributes upon these beings.

The authority, sovereignty, supremacy, and prosperity a person possesses, for instance, truly belong to Allah. As a trial, Allah grants some of his attributes to some people in this life. Attributing all the power, possessions, etc. to a person’s personality, and thus showing fear for him, would be merely associating partners with Allah. That person is neither a divine being nor someone who possesses the power to attain anything by himself. At this point, we hardly need mention that these are only imaginary beings one creates in one’s own mind. In the Qur’an it is described thus:

Behold! Truly to Allah belong all creatures, in the heavens and on earth. What do they follow who worship as His “partners” other than Allah? They follow nothing but fancy, and they do nothing but lie. (Jonah, 66)

A person who worships someone other than Allah will live to regret his delay in understanding that those partners had no virtues whatsoever. Those partners, whom they preferred to Allah in this life, will lead them to a great grief in the hereafter. Those partners are also the main reasons why pagans take Allah, Who has the sole power, honour, and glory, and Who is also the only One to be taken as the Protector, as their enemy. On the Day of Judgment, their fate will be as narrated in the following verses:

One day shall We gather them all together. Then we shall say to the idolaters, “To your place! You and those you associated with us as ‘partners’. We shall separate them, and their “partners” will say: “It was not us that you worshipped! Allah is sufficient for a witness between us and you: we certainly knew nothing of your worship of us!” There every soul will prove the fruits of the deeds it sent before it: they will be brought back to Allah their rightful Lord, and their invented falsehoods will leave them in the lurch. (Jonah 28-30)

Then they will be asked: “Where are the deities to which you gave part-worship in derogation of Allah?” They will reply: “They have left us in the lurch: Nay, we did not invoke of old, anything that had real existence.” Thus Allah leaves the unbelievers to stray. (Al-Ghafir 73-74)

The Qur’an defines the end of the pagans as follows:

But when they saw Our punishment, they said: “We believe in Allah, the one Allah and we reject the partners we used to associate with Him.” But their professing the faith when they actually saw Our punishment was not going to profit them. Such has been Allah’s way of dealing with His servants from the most ancient times. And so the rejecters of Allah perished utterly!(Al-Ghafir, 84-85)