Depending upon the nature of the religion in question a living guide may or may not be necessary at this level. For example, in Islam, our religion is based upon the direct relationship of Man and God. That which is essential for us for salvation is the practice of the five pillars which consist in Faith, Prayer, Alms, Fasting, and Pilgrimage. Provided that a person is born within a family and society that is permeated with the tradition of Islam, no guide will be necessary as these are the foundations for social life and participation at the most basic level though specific questions are often addressed to scholars and jurists concerning ethical and social problems. In the case of a personal choice to follow this religion, some form of guidance will be necessary in order to learn the canonical forms but in any case it is ultimately the responsibility of the individual to carry out the dictates of the Divine.
In many forms of Christianity on the other hand, the essential requisites of salvation consist of participation in the sacramental life of the Church. The seven primary sacraments are the Eucharist, Baptism, Confirmation, Confession, Marriage, Holy Orders, and Annointing of the Sick. The Church is a hierarchal institution and the administration of the sacraments lies within the capacity of the priesthood alone. It remains for the individual to carry these experiences with him into life outside of the Church, or we may also describe it as living constantly within the embrace of the Church, but formal participation requires the presence of an intermediary who oftentimes serves as a guide to the religious life especially in the capacity of Confessor.
It may be the case of certain special individuals that adherence to the exoteric dimension of religion is not necessary. As has been stated in the Qur'an, "He will forgive whom He will and He will punish whom He will. Allah is able to do all things." (2:284) However, it is not given to man to choose the qualifications for his own salvation. That capacity lies within God alone. Hence, it remains for us that participation in the essential exoteric observances of religion is the foundation of all spiritual life.
Although these observances are both necessary and sufficient to fulfill the primary aim of religion, there are those who, by the possession of a special capacity and inclination for knowledge, devotion, or asceticism, are called to a life that involves a greater degree of participation. For example, there are those who read the Holy Book of their religion and those who desire and possess the capacity to understand the many dimensions of its meaning; there are those who love God and those who weep for him while continually singing his praises; and there are those who not only follow God's laws but also seek to live in such a manner that befits the dignity of the manifold blessings that their Creator has bestowed upon them. These are the people who enter into the mystical dimensions of the spiritual life and who by virtue of their innate capacities are most in need of guidance to properly apply and direct them in a manner that reflects the divine will and not mere egotistical whim.
As our brother has so succinctly and eloquently stated, "In Islam, the Shariah or Law is said to be a wide well-known path that is easy to know, while the Tariqah or Spiritual Path is a narrow unmarked path that requires a guide." I am a Muslim, but I do not have experience with the Tariqah nor have I been accepted as the student of a qualified guide. As such, I cannot speak with authority on the significance of the spiritual guide, or the nature of the spiritual life in its fullness. My experience comes from being exposed to and led by those who are unqualified and who lead men into moral and spiritual error. From these experiences, and the recognition of my own limitations and infirmities, I have come to realize that instruction by a qualified teacher is needed in any attempt to pursue the esoteric dimensions of religion.
Dr. Seyyed Hossein Nasr, in the final chapter of his magisterial exposition of the tradition of Sacred Knowledge, provides us with the following description of the significance of the Master:
"There is the need for spiritual training, hence the master who has climbed the dangerous path of the cosmic mountain to its peak and who can instruct others to do the same. There is the indispensable need for a special power or grace which cannot but come from the source of the tradition in question and which can remain valid only if there is regularity of transmission or in any case access to the source of the tradition."
We can also quote from the wisdom of one of your great teachers, Black Elk, who wrote:
"It is very important for a person who wishes to 'lament' to receive aid and advice from a wichasha wakan, so that everything is done correctly, for if things are not done in the right way, something very bad can happen, and even a serpent could come and wrap itself around the 'lamenter'."