But although this comparison of society to the body is not new, it is now being more seriously and scientifically examined and pushed to its legitimate conclusions and applications. The "real meaning of the doctrine that society is an organism is that an individual has no life except that which is social, and that he cannot realize his own purposes except in realizing the larger purposes of society." All the organs of the body by which we do our work in the world and earn our bread are themselves maintained in life and fulfil the end of their own existence by working for and maintaining the whole body; and except in the common life of the body they cannot be maintained at all. It is the same with the other organs of the body. The heart, the lungs, the digestive organs, have hard and constant work to do; but only by doing it can they fulfil the very purpose of their existence and maintain themselves in life by contributing to the life of the body in which alone they can live at all. The same principle holds good in society. It is obvious in trade and commerce; a man can only maintain himself in life by helping to maintain other people. And the ideal society is one in which each man should not only yield reluctantly to the compulsion of this natural law, but should clearly see the great ends for which mankind exists and labour zealously to promote these ends, should as eagerly seek what contributes to the good of the whole as the hand is stretched out for food or as the palate relishes what stays the appetite and nourishes the whole body. Illustrating the relation of Christians to one another by the figure of the members of a body, Paul suggests several ideas.