Shari'ah
The source of Shari'ah is the Qur'an (which Muslims believe is the revealed Words of Allah, and not the product of human intellect or imagination), and the teachings and biographical example of the Prophet Muhammad, may peace be upon him (which has been meticulously recorded in a collection of books called the Hadiths [traditions].
The Qur'an is a tricky thing to interpret, because it requires us to think beyond our normal paradigm. When we succeed in doing this, we find there to be multiple levels of non-contradictory meaning that expands our awareness (especially if we look at it in the original language: English is terribly clumsy in spiritual matters and lacks subtlety and the nuances of classical Qur'anic Arabic). Unlike the Qur'an, the Hadiths are subject to revision: they were collected using a process called "isnad" to determine, through meticulous investigation, the authenticity of any given saying).
The formal bodies of interpretation of Shari'ah (and fiqh; religious jurisprudence) is not the monolithic entity that non-Muslims believe it to be. There are many schools of thought. But for the Sunni, there are four basic "madhab" (schools of thought). Each one having several variations. This does not include Shi'i schools of thought, or the various Sufi tariqah (paths / schools of thought and practice).
Scholars and thinkers in the Muslims world are divided on the question of "ijdihaad:" the interpretation of Shari'ah. Some believe that this has been sufficiently codified and must not be altered. Others believe that reinterpretation of ijdihaad is necessary.
This is where things require both logical and abstract thought. On the one hand, it's obvious how the logical and rational approach to all this must be taken. Granted, not everyone succeeds in this; but the necessity of doing so is obvious.
On the other hand, the more misunderstood, and largely forgotten, aspect of Shari'a is its spiritual dimensions. The word "Shari'ah" comes from a root word meaning "to enter a body of water and drink from it (which should remind those familiar with the Bible of John 5:1-18,). This places the entire concept of Shri'ah in a metaphysical context that has nothing to do with law or jurisprudence, and everything to do with spiritual discipline. It becomes necessary to view it simultaneously from the rational and the poetic: and find a balance between these polar opposites that unites them to form something greater than its parts.
And, of course, this is what people usually fail to accomplish, or even understand.
I should comment on the separation of church and state in Islam. As I understand it and interpret it, there is no separation of church and state in Islam for only one reason: in an authentic Islamic society, the concept of church or state do not exist in the same way that they do in other societies. The underlying concept of the church has fundamental differences from that of the mosque and its function in society; and Islam is actually expected to institute government without state (a good explanation of this will be fund in chapter 11 of Nietszche's "Thus Spake Zarathustra.") The rules by which an Islamic society govern itself are intended not only to institute social order, but to enable the enlightenment of the society and individual, and to achieve a harmony between the will and being of humanity and the Will and Being of Allah.
Also, it may interest you to know that among the aforementioned schools of thought, an amazingly large percentage of the rulings concentrate on finances, and ethical business practices. Not many people know this. The spiritual dimensions of money are all too often overlooked, to our ultimate ruin.
I also need to point out that I am convinced that there are no nations on earth that are run under authentic Shari'ah. With the exceptions of a handful of communities here and there, there are no Islamic governments anywhere on earth. I point this out, and place emphasis on it, because I know that the actions of governments and other bodies that claim to be Islamic are not in keeping with what one normally associates with God and spirituality. Many people take the wrong view of this and blame Islam, or even God Himself for this. But this is rather like expecting John Coltrane to take the blame for Kenny G. G is going to do what he does; and most of those who like his "music" lack the capacity to do better. And, most importantly, someone is making money from his intolerable and insipid dreck; and as you know, human beings will often stop at nothing to acquire money - and power.
The upshot of this is that the real Shari'ah is a code of conduct that is intended to produce a spiritual result in the physical, mental, and spiritual dimensions of an individual human being, and in the realm of human society and civilization. Human beings are not only the creation and possession of Allah (and the question of the definition of Allah is a tricky one, because there is no definition of Allah, but also the vicegerents and representatives of Allah on the earth. Preparation and sustaining this station is done through the applications of specific actions based upon authentic Divine Revelation.
For my own part, I tend to view Islam as a form of yoga or kung fu that encompasses one's physical, mental, and spiritual self, that one is doing constantly. And my intention for accepting Islam about a quarter century ago was not for cultural reasons, or even religious reasons as most would understand the idea. I was interested in finding a method by which I would find the Supreme Being and achieve an enlightened awareness of absolute reality. Of all the religions and systems, I examined (and I did my homework), Islam was the only one that provided more answers than it did questions.
After all, what good is a religious practice if it produces no spiritual result?