Furthermore, although all created things grow and develop, yet are they subjected to influences from without. For instance, the sun giveth heat, the rain nourisheth, the wind bringeth life, so that man can develop and grow. Thus it is clear that the human body is under influences from the outside, and that without those influences man could not grow. And likewise, those outside influences are subjected to other influences in their turn. For example, the growth and development of a human being is dependent upon the existence of water, and water is dependent upon the existence of rain, and rain is dependent upon the existence of clouds, and clouds are dependent upon the existence of the sun, which causeth land and sea to produce vapour, the condensation of vapour forming the clouds. Thus each one of these entities exerteth its influence and is likewise influenced in its turn. Inescapably then, the process leadeth to One Who influenceth all, and yet is influenced by none, thus severing the chain. The inner reality of that Being, however, is not known, although His effects are clear and evident. ('Abdu'l-Baha, 'Selections from the Writings of 'Abdu'l-Bahá'; compilation ‘Nature,’ prepared by the Research Department of the Universal House of Justice)
