In the Caitanya-caritamrta also, a very suitable example is given in this connection. Although the nipples on a goats neck appear to be breast nipples, they do not give milk. Similarly, material nature appears to the material scientist to act and react in a wonderful manner, but in reality it cannot act without the agitator, time, who is the representation of the Supreme Personality of Godhead. When time agitates the neutral state of material nature, material nature begins to produce varieties of manifestations. Ultimately it is said that the Supreme Personality of Godhead is the cause of creation. As a woman cannot produce children unless impregnated by a man, material nature cannot produce or manifest anything unless it is impregnated by the Supreme Personality of Godhead in the form of the time factor.