Asalamu alaykum,
There used to exist a strong trend amongst Shia scholars that nothing of the Qur’an could be understood without recourse to hadith. Interpreting Qur’an without hadith would be regarded as Tafsir BilRa’y, an exegesis based on personal whims that has been condemned by the Imams. Those that propounded this view made the Qur’an into a kind of mysterious cryptic book, that noone could understand apart from the Ahlul Bayt [a]. Today, virtually all Shia Ulema reject this notion, and believe in the authoritativeness of the apparent meaning of the Qur’an. This doesn’t mean that we don’t need the hadith of Ahlul Bayt [a] when doing Tafsir; they have the complete knowledge of the Qur’an and know it better than anyone else. What it does means is that Qur’an speaks a language that we can understand, and we are able to extract some of these meanings even if there are no narrations about the verses. The Usuli Ulema’ have given many evidences against the Akhbari position that only Ahlul Bayt can interpret the Qur’an. I will mention 2 of these. If anyone would like to research this further then I recommend the book اصول التفسير والتاويل by Sayed Kamal AlHaidary which can be downloaded here , and Zawahir AlQur’an [in english] by Sayyid Khoi which can be read here.
Proof 1: Compare the Hadith to the Qur’an
We have many authentic narrations from many of the Imams that tell us to compare the transimitted narrations to the book of Allah, and to reject those that contradict it and accept those that are supported by it. For example,
راشد عن ابي عبد الله عليه السلام قال: ما لم يوافق من الحديث القران فهو زخرف
Rashid from Abi Abdillah [a]: Any narration that isn’t inline with the Qur’an is vanity.
Wasa’il Shia 27/110
عن ابي عبد الله الصاعق عليه السلام : خطب النبي ص فقال : ايها الناس ما جائكم عني يوافق كتاب الله فانا قلته, وما جاءكم يخالف كتاب الله فلم اقله
Imam Sadiq [a]: The Prophet [sawa] addressed the people and said: O people, whatever is narrated to you from me that is inline with the Book of Allah then I have said it. And whatever is narrated to you that goes against the Book of Allah then I never said it.
Wasa’il Shia 27/111
عن ابن ابي يعفور قال سالت ابا عبد الله ع عن اختلاف الحديث يرويه من نثق ومنهم من لم نثق به؟ قال: اذا ورد عليكم حديث فوجدتم له شاهداً من كتاب الله او من قول رسول الله ص والا فالذي جاءكم به اولى به
Narrated from Ibn Abi Ya’foor: I asked Abi Abdillah [a] about the differences in narrations that are narrated by those whom we trust and those we don’t. He said: If a narration reaches you that is supported by evidence in the Book of Allah or from the sayings of the Messenger of God [sawa] (then accept it).
Wasa’il Shia 27/110
جميل بن دراج عن ابي عيد الله الصادق ع : …فما وافق كتاب الله فخذوه وما خالف كتاب الله فدعوه
Jameel ibn Draj narrated from Abi Abdillah Sadiq [a]: … whatever agrees with the Book of Allah then take it, and whatever disagrees with it then reject it.
Wasa’il Shia 27/109
These hadith and many like them clearly show that we are able to understand the Qur’an independently. If this were not the case then we would not be able to compare the hadith to the Qur’an, as understanding the Qur’an would be dependent on the hadith.
Let me make it clear that noone denies that the Ahlul Bayt [as] are needed for the most complete and correct understanding of the Qur’an, they are afterall the second of the Thaqalayn. But in same way that we can understand much of their sayings without recourse to the Qur’an, we can also understand much of the Qur’an without recourse to Ahlul Bayt.
Proof 2: The Everlasting Miracle
The miraculousness of the Qur’an is something that no Muslim denies. The Qur’an itself challenges the people many times to produce something like it:
وَإِن كُنتُمْ فِي رَيْبٍ مِّمَّا نَزَّلْنَا عَلَى عَبْدِنَا فَأْتُواْ بِسُورَةٍ مِّن مِّثْلِهِ وَادْعُواْ شُهَدَاءكُم مِّن دُونِ اللّهِ إِنْ كُنْتُمْ صَادِقِين
[2:23] And if you are in doubt as to that which We have revealed to Our servant, then produce a chapter like it and call on your witnesses besides Allah if you are truthful.
أَمْ يَقُولُونَ افْتَرَاهُ قُلْ فَأْتُواْ بِسُورَةٍ مِّثْلِهِ وَادْعُواْ مَنِ اسْتَطَعْتُم مِّن دُونِ اللّهِ إِن كُنتُمْ صَادِقِينَ
[10:38] Or do they say: He has forged it? Say: Then bring a chapter like this and invite whom you can besides Allah, if you are truthful.
أَمْ يَقُولُونَ افْتَرَاهُ قُلْ فَأْتُواْ بِعَشْرِ سُوَرٍ مِّثْلِهِ مُفْتَرَيَاتٍ وَادْعُواْ مَنِ اسْتَطَعْتُم مِّن دُونِ اللّهِ إِن كُنتُمْ صَادِقِينَ
[11:13] Or, do they say: He has forged it. Say: Then bring ten forged chapters like it and call upon whom you can besides Allah, if you are truthful
أَمْ يَقُولُونَ تَقَوَّلَهُ بَل لَّا يُؤْمِنُونَ فَلْيَأْتُوا بِحَدِيثٍ مِّثْلِهِ إِن كَانُوا صَادِقِينَ
[52:33-34] Or do they say: He has forged it. Nay! they do not believe. Then let them bring an announcement like it if they are truthful.
The question is, if only the Ahlul Bayt could understand the Qur’an, how could it be a miracle? How could it challenge people to produce something like it? For the Arabs to take this claim seriously they would have to understand the Qur’an themselves, realise its beauty and depth, but this would not be possible if its understanding was limited to a select few.
Conclusion
The above two proofs show that the Qur’an can be understood by normal people. If it could not then it wouldn’t be able to claim that it was a miracle. If it could not then the Ahlul Bayt [as] wouldn’t have instructed us to compare their sayings to the Qur’an.
Having said this, if we want to gain the greatest knowledge of the Qur’an, we need the best teachers, and these are the Ahlul Bayt. When doing tafsir of a particular verse we should read what has been transmitted from them about that verse, and look at all the verses in the Qur’an that discuss that particular subject, and then use our God given Aql to come to a conclusion.
May Allah swt grant us knowledge of His Holy Book. Ameen.
Posted by salic 
Slave of Ali 