Most people are individuals who do not have the ability to learn and engage in research and scientific work to reach a level where they may infer and deduce Islamic laws from the sources (the Quran and Sunnah) because it is not within the ability of every individual to learn their religious obligations cum their details in a demonstrative way. Neither the individuals have such a taste and talent nor does such an action serve the interest of the human society. It is like telling all people to become bakers or doctors. Obviously, if such a thing every happens, the social order will perish and there will be chaos everywhere. Therefore, in such cases there is no alternative or remedy other than Taqlid. The position is the same in regards to all other professions and specializations. In fact, there exists a kind of unwritten contract which naturally exists amongst the human beings and which is termed as "referring to a specialist".
Given that there are new cases, situations and issues emerging every day in the human society, issues that have not been dealt with by previous scholars, turning to a living jurist in matters relating to religious matters seems to be necessary and unavoidable. Therefore, we believe your act of following Mulla Sadra's doctrines in religious laws has no rational basis simply because he has no advice about newly-emerging issues.
If you ponder for a while, you will come to a clear conclusion that it is desirable for an ignorant person to refer to a knowledgeable person i.e. to do Taqlid of him because there is no contradiction between Taqlid and the verse "There is no compulsion in the religion". That is because this Quranic verse is about accepting the religion of Islam itself. As per the verse, no one is compelled to accept Islam. However, if a person knowingly and consciously accepts Islam (or any other religion), naturally he must abide by all its principles, rules and codes.
When it comes to sermon 18 of Nahj al-Balaghah, the Commander of the Faithful, Ali (a.s.) presents strong arguments to substantiate the invalidity of reasoning independently of the Quran and Sunnah. With a precise categorization of Ijtihad in the said meaning which is based on five pillars, the Imam explicates the falseness of this attitude. His sayings, if understood properly, do not have anything to do with the Ijtihad which is based on sound principles and foundations.
The aforementioned question is surrounded by some complications and ambiguities which must be dealt with properly. The questions which revolve around those ambiguities are the following:
1. Who should follow a Mujtahid?
2. In what religious matters should we follow a Mujtahid?
3. Whom should we follow?
4. What kind of Taqlid has been denounced?
5. Is the sentence "There is no compulsion in the religion" opposed to the necessity of Taqlid?
6. If Taqlid is in order, then why has Imam Ali (a.s.) denounced in sermon 18 of Nahj al-Balaghah?
Now, we will follow the above sequence in our answers to the questions:
First: In a general division, the duty-bounds (mukallafin) are divided into two groups:
a) People who have attained a level of knowledge through education, research and scientific endeavor where they can deduce divine laws and their obligations from the Islamic sources i.e. the Quran and the Sunnah of the Prophet.
b) People who have not been able to attain a level of knowledge through education, research and scientific endeavor where they can deduce divine laws and their obligations from the sources (book and Sunnah).
Obviously, based on the command of the intellect ('aql) and the conduct of wise men and women, the first group of people cannot turn to other people in matters about which they have knowledge. As for the second group, considering that most people are in this category, it is not possible for all people to learn their religious duties in a demonstrative manner because neither the individuals have such a potentiality and talent nor does it serve the general interest of the human society. It is like telling all people to become bakers or doctors which obviously will lead to destruction of social order and prevalence of chaos in the human society. Therefore, in such cases there is no alternative or remedy other than Taqlid. This rule holds good and is applicable to all other professions and specializations. In fact, there is a kind of unwritten contract which naturally exists amongst the human beings and which is termed as referring to a specialist.
For further information about the necessity of Taqlid see the answers which are available on this website. See index "The Philosophy of Taqlid from the Maraji' and the Unexplained Proofs" No.2991 and index "The Reasons behind the Necessity of Following the Maraji'" No. 1078.
Given that you have said that you are a follower of the Ja'fari School and you are following the Islamic rules with reliance on the doctrines introduced by Mulla Sadra, we believe by so doing you have also in reality accepted the legality of Taqlid.
Second: Muslim scholars divide religious doctrines into two categories:
a) Those having to do with the mind and heart i.e. doctrines relating to faith and beliefs which in the Islamic terminology are called the "principles of religion".
b) Those having to do with the limbs i.e the doctrines relating to action which in Islamic terminology are called the branches of the religion. They include the practical laws of Islam.
Muslim scholars have unanimously said that in the fundamentals of faith; a person must believe in them with his own insight and understanding. He cannot follow others in matters relating to the roots and principles of faith. For further information about the impermissibility of Taqlid in the fundamentals of faith, see the answers available on this website. See index "Taqlid in Beliefs" No.4809 and index "Taqlid in the Principles of Religion" No.1460.
You have said that you are a follower of the Ja'fari School and that you are acting upon the religious rules with reliance on Mulla Sadra's doctrines. If you are following him in the branches of faith, it is the same as Taqlid of Maraji' of which you are running away.
Here we shall deal with the answer to the third question: Is Taqlid of a dead Mujtahid permissible or not?
In view of the fact that there are new cases and issues emerging every day in the human society, issues that have not been dealt with by previous scholars, turning to a living jurist in matters relating to religious matters seems to be necessary. Therefore, your act of following Mulla Sadra in religious laws has no rational basis.
For further information about the necessity of following a living Mujtahid, see answers that are available on this website. Vide index "The Benefits of Doing Taqlid of a Living Mujtahid", No.539.
Fourth: Without doubt, Taqlid in some branches of faith is also not good. Balkhi Rumi says in his famous poem as such:
Khalq ra taqlid shan bar baad daad
Ay doosad la'nat bar ein taqlid baad.
[The people were destroyed owing to their blind imitation. May a thousand curses be upon such an imitation.]
We should see as to what kind of Taqlid is it that has been denounced and reproached. In order to get a clear answer to this question, it is necessary to make mention and assessment of the various types of Taqlid and then pass judgment about each one of them.
There are four types of Taqlid which are enumerated as under:
a) A knowledgeable person following (doing Taqlid of) another knowledgeable person;
b) An ignorant individual following another ignorant individual;
c) A knowledgeable person following an ignorant one;
d) An ignorant individual following a learned and knowledgeable person;
If you ponder for a while, you will understand that all the four types of Taqlid are unacceptable except for the fourth one. The first case is like preferring something without a point of preference, something the wise men and women do not accept.
The second type is futile and fruitless.
The third type is not fruitless yet it is rationally mean and abominable. For this reason, it is only the fourth case which is not denounced and which every wise man and woman accept.
As for the fifth question, we will suffice to two answers to it. The first answer is that there is no dichotomy between Taqlid and "There is no compulsion in the religion" That is because the Quranic verse is about accepting the religion of Islam itself. As per the verse, no one is compelled to accept Islam. However, if a person knowingly and consciously accepts Islam (or any other religion), naturally he must abide by all its principles, rules and codes.
To clarify this point, we shall present an example.
Just imagine that each one of us is not compelled to become a member of the military force. There is no one compelling us to enter the military. Naturally, we are under no compulsion in regards to military programs like morning drills, manures etc. This is until we have not become a member. Once we accept its membership of our own choice and free will, we must abide by its rules and regulations. Then it is not wise to say that we have no commitment towards the military programs; we cannot say that we can act freely because by accepting its membership, we have also agreed to remain committed and obedient.
Second answer: Can a person who has accepted Islam of his own free choice say "I will not keep fast because there is no compulsion in the religion; I will not offer prayer because there is no compulsion in the religion; (In case of financial capability,) I will not perform Hajj because there is no compulsion in the religion and if I am liable to poordue (zakat), I will not pay it because there is no compulsion in the religion and so on and so forth?
Imam Ali's Criticism of the Difference in the Opinions of Jurists
Based on foregoing discussion, it has become clear that Taqlid is rational. The same is understood from the traditions also. Here we mention two traditions confirming our stand about Taqlid:
A) Salim bin Abi Hayyah says: "I was in the company of Imam Sadiq (a.s), and when I wanted to leave his company I asked him to advise me. The Imam said: Go to Aban bin Tahglib. He has heard a lot hadiths from me. You should quote on my behalf whatever he narrates for you.
B) Imam has been narrated as having said to Aban: "Sit in the mosque and give fatwa to people. I like people like you to be amongst our followers."
Our question to you is that who should Aban give fatwa to? In case he gives fatwa, what is the duty of the people towards his fatwas? Should the people accept them? Is it something different from Taqlid? Is it not that an ignorant individual should refer to a knowledgeable person to seek his advice, which we term as "Taqlid"?
Now that some are supposed to give fatwa, naturally a jurist's understanding of Quranic and narrative sources should be accepted as a criterion and in this case differences in the fatwas are very natural. In this regard, see index: "The Foundations of Issuing Fatwa, Question No. 524.
When it comes to sermon 18 of Nahj al-Balaghah, Imam Ali's statement becomes clear in the light of the foregoing explanations. The Imam presents strong arguments to substantiate the invalidity of reasoning or Ijtihad or simply legislation with reliance on one's own view. With a precise categorization of Ijtihad in the said meaning which is based on five pillars, the Imam explicates the falseness of this attitude. His sayings, if understood properly, do not have anything to do with the Ijtihad which is based on sound principles and foundations.
In other words, with his expressive words and precise analysis, the Imam renders void what is known as analogy, istihsan (juristic preference), itjihad on one's formed opinion. Thus, he leaves no way open to their proponents because God, the Exalted has revealed a perfect religion. The Quran is complete and comprehensive addressing all human needs. Moreover, the Prophet of Islam (pbuh) made every effort to preach and propagate Islam, and God does not want mankind to be disunited and dispersed. It has called upon all human beings to be united.
 - In addition, Mulla Sadra does not have a book on the practical laws of Islam.
 - Balkhi, Mawlana Jaluddin Muhammad, Mathnawi Ma'navi (Spiritual Couplets), second copy, pg.204, Bulaq Publication, 1835.
 - Noori, Mustadrak al-Wasail, vol.17, pg.315, hadith14-21452, Aalulbayt Institute, Qom, 1408 A.H.
 - Makarem Shirazi, Naser, The Imam's Message a Comprehensive Exposition of Nahj al-Balaghah, vol.1, pg.624, Darul Kutub al-Islamiyah, Tehran, first edition, 1986.
 - Ibid, vol.1, pg. 628.