Knowledge and heart are just like the positive and negative forces; it is these two things which make life balanced. If the heart quality is very strong and intellect is lacking then life lacks balance. Knowledge and heart quality must be developed together. And therefore according to Attar the faculty of devotion or quality of heart is the second valley, the Valley of Love; and the third valley is the Valley of Knowledge, the knowledge which illuminates and comes by the help of the love element and the intellect. That is the knowledge which is called spiritual knowledge. Without a developed love quality man is incapable of having that knowledge. There are fine lights and shades in one's life which cannot be perceived and fully understood without having touched the deeper side of life, which is the devotional side. The person who has never in his life been wholly grateful cannot know what it is. He who has not experienced humility in life does not know its beauty. The one who has not known gentleness or modesty cannot appreciate its beauty or recognize it.