The mental consciousness of the human individual seeks to analyze and fragment everything into component parts and to separate everything into distinct categories. When the human mind therefore looks at the various paths of Yoga, it focuses on the differences of methodology and stages, rather than on the unifying common basis.
Sri Aurobindo quickly reviews the differences between the various primary paths: “…the Hathayogic process is psycho-physical, the Rajayogic mental and psychic, the way of knowledge is spiritual and cognitive, the way of devotion spiritual, emotional and aesthetic, the way of works spiritual and dynamic by action. Each is guided in the ways of its own characteristic power.”
While these powers may take different forms, appropriate to the specific level or plane on which they operate, they all originate from the same source and are rooted in the same power. “But all power is in the end one, all power is really soul-power. In the ordinary process of life, body and mind this truth is quite obscured by the dispersed, dividing and distributive action of Nature which is the normal condition of all our functionings, although even there it is in the end evident; for all material energy contains hidden the vital, mental, psychic, spiritual energy and in the end it must release these forms of the one Shakti, the vital energy conceals and liberates into action all the other forms, the mental supporting itself on the life and body and their powers and functionings contains undeveloped or only partially developed the psychic and the spiritual power of the being.”
As the seeker who practices one or the other of the paths progresses along the way, there comes a time when results that are usually associated with one of the other paths begin to manifest. “Therefore the Hathayogic process has too its pure psychic and spiritual result, the Rajayogic arrives by psychic means at a spiritual consummation. The triple way may appear to be altogether mental and spiritual in its way of seeking and its objectives, but it can be attended by results more characteristic of the other paths, which offer themselves in a spontaneous and involuntary flowering, and for the same reason, because soul-power is all-power and where it reaches its height in one direction its other possibilities also begin to show themselves in fact or in incipient potentiality.”
For Sri Aurobindo, it is just this underlying unity behind all the different apparent forms of power that provides a rationale for the type of integral Yoga that he envisions: “This unity at once suggests the possibility of a synthetic Yoga.”
Sri Aurobindo, The Synthesis of Yoga, Part Four: The Yoga of Self-Perfection, Chapter 1, The Principle of the Integral Yoga, pp. 584-585