What is this spirit in man that urges him forever to depart from happiness and security, to toil, to place himself in danger, even to risk a reasonable certainty of death? It dawned upon me up there in the moon as a thing I ought always to have known, that man is not made simply to go about being safe and comfortable and well fed and amused. Against his interest, against his happiness he is constantly being driven to do unreasonable things. Some force not himself impels him and go he must.