Sri Aurobindo has defined the 4 main lines of development as occultism, religion, philosophy and spiritual realisation. Each one of these has its rationale in the spiritual evolution as it speaks to a need of our nature and the development it is undergoing.
Sri Aurobindo explains: “There are four necessities of man’s self-expansin if he is not to remain this being of the surface ignorance seeking obscurely after the truth of things and collecting and systematising fragments and sections of knowledge…”
“He must know himself and discover and utliise all his potentialities: but to know himself and the world completely he must go behind his own and its exterior, he must dive deep below his own mental surface and the physical surface of Nature. This he can only do by knowing his inner mental, vital, physical and psychic being and its powers and movements and the universal laws and processes of the occult Mind and Life which stand behind the material front of the universe: that is the field of occultism…”
“He must know also the hidden Power or Powers that control the world: if there is a Cosmic Self or Spirit or a Creator, he must be able to enter into relation with It or Him and be able to remain in whatever contact or communion is possible….. this approach is the aim of religion: its purpose is to link the human with the Divine and in so doing sublimate the thought and life and flesh so that they may admit the rule of the soul and spirit.”
“But this knowledge must be something more than a creed or a mystic revelation; his thinking mind must be able to accept it, to correlate it with the principle of things and the observed truth of the universe: this is the work of philosophy, and in the field of the truth of the spirit it can only be done by a spiritual philosophy, whether intellectual in its method or intuitive.”
“But all knowledge and endeavor can reach its fruition only if it is turned into experience and has become a part of the consciousness and its established operations; in the spiritual field all this religious, occult or philosophical knowledge and endeavor must, to bear fruition, end in an opening up of the spiritual consciousness, in experiences that found and continually heighten, expand and enrich that consciousness and in the building of a life and action that is in conformity with the truth of the spirit: this is the work of spiritual realisation and experience.”
Sri Aurobindo, The Life Divine, Book 2, Part 2, Chapter 24, “The Evolution of the Spiritual Man”