Such, then, according to Macvicar, is the nature of mind or spirit. It is a being so constituted as to be at once in possession of ideas, and so far fixed; and also in possession of undetermined life or activity, and so far free. These are, as it were, the opposite poles of its being, and the conditions of its activity. If either is wanting, the other vanishes. Without something fixed in the mind, some object of thought or feeling, there can be no thinking or feeling. Without something unfixed there can be nothing to think or to feel with, much less can there be any thinking or feeling of self--that is, self-consciousness. But, grant this condition in the individual, and add the law of assimilation, operating first from God above, thus giving reason and conscience, on the higher aspect of our being; and, secondly, from nature around, thus giving observation and instincts harmonious with our situation in the system of the universe, and then human nature emerges. But human nature plainly belongs to the last day of the work of creation rather than the first, where we are now. In man, to all appearance, the organism is the mother and nurse of the spirit. And though the assimilative action of the mind upon the body becomes normally, at least, stronger and stronger as life advances, so long as the organ retains all its perfection, yet at first the assimilative action of the body upon the mind is almost everything. The infant, the child, is little else but the victim of sensation--that is, of assimilations in its mind, effected by the force of external nature, including the organism itself. But as the mind, through the sustained action towards the focus of the myo-neuro-cerebral system, which is in the brain, gains quantity or intensity--in one word, energy--it becomes more independent and free, and more able to react out of itself upon the organism in any direction of which it makes choice....