This is the rational and philosophic side of Yoga and very difficult, but I will take you slowly through it.
Yoga means the method of joining man and God. When you understand this, you can go on with your own definitions of man and God, and you will find the term Yoga fits in with every definition. Remember always, there are different Yogas for different minds, and that if one does not suit you, another may. All religions are divided into theory and practice. The Western mind has given itself up to the theory and only sees the practical part of religion as good works. Yoga is the practical part of religion and shows that religion is a practical power apart from good works.
At the beginning of the nineteenth century man tried to find God through reason, and Deism was the result. What little was left of God by this process was destroyed by Darwinism and Millism. Men were then thrown back upon historical and comparative religion. They thought, religion was derived from element worship (see Max Müller on the sun myths etc.); others thought that religion was derived from ancestor worship (see Herbert Spencer). But taken as a whole, these methods have proved a failure. Man cannot get at Truth by external methods.
"If I know one lump of clay, I know the whole mass of clay." The universe is all built on the same plan. The individual is only a part, like the lump of clay. If we know the human soul — which is one atom — its beginning and general history, we know the whole of nature. Birth, growth, development, decay, death — this is the sequence in all nature and is the same in the plant and the man. The difference is only in time. The whole cycle may be completed in one case in a day, in the other in three score years and ten; the methods are the same. The only way to reach a sure analysis of the universe is by the analysis of our own minds. A proper psychology is essential to the understanding of religion. To reach Truth by reason alone is impossible, because imperfect reason cannot study its own fundamental basis. Therefore the only way to study the mind is to get at facts, and then intellect will arrange them and deduce the principles. The intellect has to build the house; but it cannot do so without bricks and it cannot make bricks. Jnana-Yoga is the surest way of arriving at facts.
First we have the physiology of mind. We have organs of the senses, which are divided into organs of action and organs of perception. By organs I do not mean the external sense-instruments. The ophthalmic centre in the brain is the organ of sight, not the eye alone. So with every organ, the function is internal. Only when the mind reacts, is the object truly perceived. The sensory and motor nerves are necessary to perception.
Then there is the mind itself. It is like a smooth lake which when struck, say by a stone, vibrates. The vibrations gather together and react on the stone, and all through the lake they will spread and be felt. The mind is like the lake; it is constantly being set in vibrations, which leave an impression on the mind; and the idea of the Ego, or personal self, the "I", is the result of these impressions. This "I" therefore is only the very rapid transmission of force and is in itself no reality.
The mind-stuff is a very fine material instrument used for taking up the Prâna. When a man dies, the body dies; but a little bit of the mind, the seed, is left when all else is shattered; and this is the seed of the new body called by St. Paul "the spiritual body". This theory of the materiality of the mind accords with all modern theories. The idiot is lacking in intelligence because his mind-stuff is injured. Intelligence cannot be in matter nor can it be produced by any combinations of matter. Where then is intelligence? It is behind matter; it is the Jiva, the real Self, working through the instrument of matter. Transmission of force is not possible without matter, and as the Jiva cannot travel alone, some part of mind is left as a transmitting medium when all else is shattered by death.
How are perceptions made? The wall opposite sends an impression to me, but I do not see the wall until my mind reacts, that is to say, the mind cannot know the wall by mere sight. The reaction that enables the mind to get a perception of the wall is an intellectual process. In this way the whole universe is seen through our eyes plus mind (or perceptive faculty); it is necessarily coloured by our own individual tendencies. The real wall, or the real universe, is outside the mind, and is unknown and unknowable. Call this universe X, and our statement is that the seen universe is X plus mind.
What is true of the external must also apply to the internal world. Mind also wants to know itself, but this Self can only be known through the medium of the mind and is, like the wall, unknown. This self we may call Y. and the statement would then be, Y plus mind is the inner self. Kant was the first to arrive at this analysis of mind, but it was long ago stated in the Vedas. We have thus, as it were, mind standing between X and Y and reacting on both.
If X is unknown, then any qualities we give to it are only derived from our own mind. Time, space, and causation are the three conditions through which mind perceives. Time is the condition for the transmission of thought, and space for the vibration of grosser matter. Causation is the sequence in which vibrations come. Mind can only cognise through these. Anything therefore, beyond mind must be beyond time, space, and causation.
To the blind man the world is perceived by touch and sound. To us with five senses it is another world. If any of us developed an electric sense and the faculty seeing electric waves, the world would appear different. Yet the world, as the X to all of these, is still the same. As each one brings his own mind, he sees his own world. There is X plus one sense; X plus two senses, up to five, as we know humanity. The result is constantly varied, yet X remains always unchanged. Y is also beyond our minds and beyond time, space, and causation.
But, you may ask, "How do we know there are two things (X and Y) beyond time, space, and causation?" Quite true, time makes differentiation, so that, as both are really beyond time, they must be really one. When mind sees this one, it calls it variously — X, when it is the outside world, and Y, when it is the inside world. This unit exists and is looked at through the lens of minds.
The Being of perfect nature, universally appearing to us, is God, is Absolute. The undifferentiated is the perfect condition; all others must be lower and not permanent.
What makes the undifferentiated appear differentiated to mind? This is the same kind of question as what is the origin of evil and free will? The question itself is contradictory and impossible, because the question takes for granted cause and effect. There is no cause and effect in the undifferentiated; the question assumes that the undifferentiated is in the same condition as the differentiated. "Whys" and "wherefores" are in mind only. The Self is beyond causation, and It alone is free. Its light it is which percolates through every form of mind. With every action I assert I am free, and yet every action proves that I am bound. The real Self is free, yet when mixed with mind and body, It is not free. The will is the first manifestation of the real Self; the first limitation therefore of this real Self is the will. Will is a compound of Self and mind. Now, no compound can be permanent, so that when we will to live, we must die. Immortal life is a contradiction in terms, for life, being a compound, cannot be immortal. True Being is undifferentiated and eternal. How does this Perfect Being become mixed up with will, mind, thought — all defective things? It never has become mixed. You are the real you (the Y of our former statement); you never were will; you never have changed; you as a person never existed; It is illusion. Then on what, you will say, do the phenomena of illusion rest? This is a bad question. Illusion never rests on Truth, but only on illusion. Everything struggles to go back to what was before these illusions, to be free in fact. What then is the value of life? It is to give us experience. Does this view do away with evolution? On the contrary, it explains it. It is really the process of refinement of matter allowing the real Self to manifest Itself. It is as if a screen or a veil were between us and some other object. The object becomes clear as the screen is gradually withdrawn. The question is simply one of manifestation of the higher Self.