'All these therefore (beginning with mind and ending in sacrifice) centre in will, consist of will, abide in will. Heaven and earth willed, air and ether willed, water and fire willed. Through the will of heaven and earth &c. rain wills; through the will of rain food wills; through the will of food the vital airs will; through the will of the vital airs the sacred hymns will; through the will of the sacred hymns the sacrifices will; through the will of the sacrifices the world (as their reward) wills; through the will of the world everything wills. This is will. Meditate on will.
In plain words: Everything from thinking to ritual rests on will. The teacher describes the whole world as a chain of intention: sky and earth lead to rain, rain to food, food to life, and so on until everything has its purpose.