God does work through both pure and impure vessels but that does not mean that one should keep nature impure for ever. When the vessel will become pure the urge for action coming from within will be a flawless, definitive action. As long as that does not happen one has to minimize one's activities.
As often as Herman had witnessed the slaughter of animals and fish, he always had the same thought: in their behaviour toward creatures, all men were Nazis. The smugness with which man could do with other species as he pleased exemplified the most extreme racist theories, the principle that might is right.
To be free from all egoistic motive, careful of truth in speech and action, void of self-will and self-assertion, watchful in all things, is the condition for being a flawless servant.
What is required is faith. Man has body, life and mind but that is not all that constitutes man. He has risen to the mind as a result of evolution. Now a higher consciousness will be evolved - this I call Supermind. It is the instrument of the Divine Consciousness, the Truth-Consciousness.
India saw from the beginning, - and, even in her ages of reason and her age of increasing ignorance, she never lost hold of the insight, - that life cannot be rightly seen in the sole light, cannot be perfectly lived in the sole power of its externalities.
There is a veil between the Supermind above and the lower Prakriti below - the veil of ingrained formations. This veil may completely withdraw or be partially withdrawn. Thus even if there is some little opening, with the contact of Light from above the lower nature will get slowly changed.
Thus to act under the guidance coming from above, this is one side of the sadhana, the dynamic side. The other one is the discrimination between the Purusha and the Prakriti. The Purusha will calmly observe, give sanction, choose, but will realise that all this does not belong to him - all these are outside him. This is the static side of the sadhana. These two aspects constitute the basis of Yoga.
What do you want to do sadhana for? The aim should not be the satisfaction of egoism: "I want to be a great yogi; I shall have so much power and with that power I shall establish myself in the world." All such thoughts must be thrown far away.