The cow is the symbol of the Light of the higher consciousness descending turning all into the Truth-light.
The cow usually means the Higher Consciousness. The cow in the occult symbolism indicates Light or the consciousness — white indicates the purified or spiritual consciousness — the white Light. The white cow is the pure consciousness in which there is the Light.
The cow stood for light because the word 'go' meant both ray and cow, and because the cow was their most precious possession which maintained their life and was constantly in danger of being robbed and concealed. But once created, such a symbol becomes alive. The Rishis vitalised it and it became a part of their realisation. It appeared in their visions as an image of spiritual light.
There are always two methods of living in the Supreme. One is to draw away the participation of the consciousness from things altogether and go so much inwards as to be separated from existence and live in contact with that which is beyond it. The other is to get to that which is the true Essence of all things, not allowing oneself to be absorbed and entangled by the external forms. Desire, attachment, slavery to the attractions of the external sense are the chief obstacle to this movement, so in either way they have to be got rid of. But it is quite possible to see the Supreme before the attraction of external sense is gone, only one cannot live securely in It if there is desire and external attachment because that is always taking one away from the inner poise.
His being lay down in bright immobile peace
And bathed in wells of pure spiritual light;
It wandered in wide fields of wisdom-self
Lit by the rays of an everlasting sun.
Even his body's subtle self within
Could raise the earthly parts towards higher things
And feel on it the breath of heavenlier air.