The strife of parties and sects was itself part of a still wider process; and this process must be recognised as the most important single condition of that widening of the sphere of imaginative sympathy which has been the root cause of the improvement of social organisation, of the general increase of liberty, and thus of the progress of the modern nations. This wider process is the general increase of human intercourse, both within nations and between them. Only so long as men know little of one another, can they continue to regard one another with entire hostility or cold indifference. The knowledge and understanding brought by personal intercourse is necessary to sympathy; but as soon as, and in proportion as, such knowledge is acquired, the innate social tendencies common to all men are brought into play. As soon as man understands that his fellow man suffers the same pains and joys as himself, longs for the same goods, fears the same evils, throbs with the same emotions and desires, then he shares with him in some degree these feelings, in virtue of that fundamental law of all social beings, the law of primitive sympathy; then also pity and sympathetic sorrow and tender regard are awakened in his breast; then his fellow man is no longer the object of his cold or hostile glances, as a certain rival and probable enemy, but is seen to be a fellow toiler and sufferer whom he is willing to succour, a fellow creature whose joys and sorrows alike he cannot but share in some degree. Increasing freedom of intercourse throughout the civilised world, and beyond its boundaries also, has been the most characteristic feature of the age of progress, and in it we may recognise the most fundamental condition of that progress. Science and mechanical invention have been the means by which this greater freedom of intercourse has been brought about. First and most important perhaps was the invention of printing, the consequent spread of the habit of reading, and the wide diffusion of the written word. Second only to this was the improvement of the art of navigation, which brought the remotest peoples of the world within the ken of Europe and greatly promoted the intercourse of the European peoples, as well as the circulation of persons and news within each nation; for the development of commerce over seas implies a corresponding development of commerce within the national boundaries. Then came the use of steam in locomotion on sea and land, the press and the telegraph; and, with the advent of these, intercourse within and without became really free and abundant; mutual knowledge and understanding between men and nations grew rapidly, and the age of progress was assured.