In general it can be said that all Shari'ah laws are based on divine knowledge and wisdom and the benefits and indecencies of every ruling has been explained and established, and no one other than Allah, the Most High has complete awareness of them. The reasons for some of the laws have been mentioned in the Quran and traditions but it does not imply or state that they are the real causes of the jurisprudential law. In fact, they are meant to explain a theological and ideological matter to us in the sense that God did not create the laws in order that He Himself benefit from them. In fact, divine legislations are intended for the benefit of man. In other words, there is wisdom behind every divine law and juridical rule.
What has been related as a reason for the prohibition of pork is a Quranic verse which we should accept with absolute obedience. The Quran says, «فَإِنَّهُ رِجْسٌ» "it is unclean". God has stated the reason in a general way which enjoys rational and ideological support. Despite its generality, the verse makes mention of the foulness and uncleanness of pig meat which is the main reason for prohibition of pork. In short, the prohibition of pork is evidenced by Quranic verses and traditions which must be accepted with absolute submission. Some of the reasons mentioned for the prohibition of pork are things that have been discovered and revealed to man while it is possible that some other harms of pork be discovered in future.
In order for the answer to be clarified, it is necessary to make mention of the following points:
1) In general it can be said that all religious laws are based on divine knowledge and wisdom and the benefits and indecencies of every ruling has been explained and established, and no one other than Allah, the Most High has complete awareness of them. The human sciences are also capable of finding out some of the reasons and rationales of the Islamic laws, not all of them.
2) In order to act upon the Islamic law, it is not necessary to have knowledge of the benefits and indecencies (evil). It is necessary to abide by divine injunctions even if you do not know their philosophy and rationale. However, our adherence to divine laws does not mean that we should surrender ourselves to God without any intellection. There is no objection to asking about the philosophy of religious laws. Additionally, it is pure rationality to follow someone who has knowledge of good and evil, decency and indecency.
3) The reasons and wisdom mentioned by traditions do not explain the jurisprudential laws nor do they imply that they are the only causes of the juridical law. In fact, they are meant to explain a theological and ideological matter to us in the sense that God did not create the laws in order that He Himself benefit from them. Divine legislations are intended for the benefit of man. In other words, the divine laws enjoy a standard or criterion. Therefore, making mention of some of the reasons and philosophies or the benefits and harms do not means we should accept them as the whole and sole causes of the laws as there might some other underlying reasons of which we are unaware and which have not been mentioned to us.
What actually serves as a reason for jurisprudential deductions is that God or His Prophet (s) has stated in a general way that "inflicting harm upon oneself" is haram. There are traditions in this regard and God or His Prophet (s) also means to explain the same instruction. If they point out some instances of harmful things, it does necessarily mean that the harm is the cause for prohibition, rather the aim is to make mention of an ideological point as was stated above. Therefore, one cannot say that an instance of a harm mentioned by the Quran or tradition is the cause of prohibition; in fact some of the harms may signify prohibition and some others signify abominableness.
4) Despite the fact that God, the Sublime, has bestowed profuse bounties upon man and placed those bounties at his disposal, He also created some limitations and boundaries in accord with proper standards and human nature.
5) Pigs are considered as essentially impure (najis-ul 'ayn) animals and all parts of a pig's body are najis and it is haram to eat its meat.
Hence, in view of the above we say:
a) When it comes to the wisdom and philosophy of the prohibition of "pork", it is necessary that the reasons be mentioned in minute details and if the reasons are mentioned in such a way, one cannot say that they are the real cause of the prohibition of pork because what serves as a reason for prohibition of pork according to Fiqh (jurisprudential viewpoint) is a Quranic verse which we should accept with absolute obedience. The Quran says,«فَإِنَّهُ رِجْسٌ». In this verse, God has stated the reason in a general way which enjoys rational and ideological support. Despite its generality, the verse makes mention of the foulness and uncleanness of pig meat as well as the harm which it entails and which is the main reason for prohibition of pork.
In any case, different benefits and harms have been stated for pork. For example, it has been reported in a tradition that Imam Reza (a.s) considered pork among the things that are harmful to man's body. Also, when God transformed a tribe because of their sins, He turned them into animals including pigs.
3. The prohibition of pork and its essential impurity is not because of its worthlessness so that we may dispose of it in any way we want. For this reason, it has been narrated that one day when a man killed a pig, Imam Ali (a.s.) guaranteed the payment of its price to its owner. Definitely, the guarantee for repayment of the pig's price is in no way dichotomous with its prohibition and impurity in Islamic Shari'ah. In fact, the Imam's saying implies that this animal is valuable for its non-Muslim owner. Therefore, it is not permissible to destroy or transgress upon other peoples' property.
In short, the prohibition of pork is evidenced by Quranic verses and traditions which must be accepted with absolute submission. Some of the reasons mentioned for the prohibition of pork are things that have been discovered and revealed to man while it is possible that some other harms of pork be discovered in future.
 - Vide: The Philosophy and Wisdom behind Jurisprudential laws; 8593 (site: 9135)
 - Vide indexes "The Philosophy of the Prohibition of Gold," question 759 (site: 799); "The Philosophy of Undesirability of Eating Cheese", 1538 (site: 1550); "The Wisdom and Philosophy of Entering a Mosque with the Right Foot", question 5414 (site: 5849); "The Philosophy of Penalty according to Islam", question 13138 (site: 12805); and other indexes on Islamquest.net about the philosophy of Shari'ah Laws.
 - For example, Imam Redha (a.s.) said:
«اعْلَمْ یَرْحَمُکَ اللَّهُ أَنَّ اللَّهَ تَبَارَکَ وَ تَعَالَى لَمْ یُبِحْ أَکْلًا وَ لَا شُرْباً إِلَّا مَا فِیهِ مِنَ الْمَنْفَعَةِ وَ الصَّلَاحِ وَ لَمْ یُحَرِّمْ إِلَّا مَا فِیهِ الضَّرَرُ وَ التَّلَفُ وَ الْفَسَادُ فَکُلُّ نَافِعٍ مُقَوٍّ لِلْجِسْمِ فِیهِ قُوَّةٌ لِلْبَدَنِ فَحَلَالٌ وَ کُلُ مُضِرٍّ یَذْهَبُ بِالْقُوَّةِ أَوْ قَاتِلٍ فَحَرَامٌ»
May Allah bless you, you should know that everything which is forbidden is due to its harmfulness, therefore all harmful things are forbidden. Everything that is beneficial is permitted. So all permitted things are beneficial. God did not forbid a thing except that there was harm, loss and evil in it. Therefore everything that has a benefit for the body and strengthens the body is halal and everything that destroys the strength or is a killer is haram." Majlisi, Muhammad Baqir, Behar al-Anwar, vol.62, pg. 166, Dar Ihya al-Turath al-Arabi, Beirut, 2nd edition, 1403 A.H.
 Imam Khomeini, Sayyid Rohullah, Tawzih al-Masail (with annotation), vol.1, pg. 75, Islamic Publications Office, Qom, 8th edition, 1424 A.H.
 - The Holy Quran says in Sura Al-Ana'am verse 145: " Say: "I find not in the message received by me by inspiration any (meat) forbidden to be eaten by one who wishes to eat it, unless it be dead meat, or blood poured forth, or the flesh of swine,- for it is an abomination - or, what is impious, (unclean meat)."
 - Sura Al-Ana'am verse 145: "The flesh of swine is unclean (or foul)."
 - Behar al-Anwar, vol.62, pg. 166; Also, in this regard you can refer to: Shaykh Saduq, 'Elal al-Sharaye', vol.2, pg. 483 – 485, Dawari Book Store, Qom, 1st edition, 1385 (2006).
 - 'Elal al-Sharaye', vol.2, pg. 484
 - Kulayni, Muhammad bin Ya'qub, Al-Kafi, researched and edited by Ghaffari, Ali Akbari and Akhundi, Muhammad, vol.7, pg. 368, Dar al-Kutub al-Islamiyah, Tehran, 1407 A.H.