Very often people who are lacking in knowledge and have more strength than is necessary, destroy their own purpose. While wanting to construct they cause destruction. The greatest fault of human nature is that every man thinks that he knows best. When he speaks to another he thinks that the latter knows but half; and when he is speaking about a third person he thinks that that person knows only a quarter. Some few who do not rely upon their knowledge are then dependent upon the advice of others; therefore their success or failure, and also their thinking, depend upon the advice of others. It is most difficult in life to possess power and knowledge, and together with these to have clear vision. And the best way of keeping the vision clear is by retaining the balance between power and knowledge.