Sri Aurobindo
Letters of Sri Aurobindo
Volume III - Part 4
When a higher force comes down into a lower plane, it is diminished and modified by the inferior substance, lesser power and more mixed movements of that lower plane. Thus, if the Overmind Power works through the illumined mind, only part 
of its truth and force can manifest and be effective – so much only as can get through this less receptive consciousness. And even what gets through is less true, mixed with other matter, less overmental, more easily modified into something that is part truth, part error. When this diminished indirect Force descends farther down into the mind and vital, it has still something of the Overmind creative Truth in it, but gets very badly mixed with mental and vital formations that disfigure it and make it half effective only, sometimes ineffective.