“It is the characteristic of error to be feeble, fluctuating, and anxious: it is the property of truth to be constant in the unity of its perceptions, and calm in the consciousness of its own power. The assailant who is ever attacking, and ever changing the ground of his attack, may prove his anxiety, his vigilance, the hostility of his purpose, and the boldness of his daring; but he will also prove the weakness of his own resources, and the impregnable resistance of that which he is seeking to overthrow.”