"It has ever been my opinion that the essential features of a man's nature cannot be changed; he may give up errors — he may change from virtuous and good habits to vicious courses; but the natural bent of his disposition, whether devoted to active employment or inward contemplation — whether impetuous or gentle — whether penetrating to the hidden depths of things, or resting satisfied with superficial views — whether acting in the affairs of life with a firm and powerful grasp or with weakness — ever remains from childhood to death the same."