The existing hypotheses that describe the nature of ball lightning are analyzed by an approach based on the elementary processes that occur in this lightning. It is shown that the internal energy stored in the ball lightning can be retained in it during the observed time only if this energy is chemical in nature. The chemical reactions and radiation processes that occur in excited air are investigated. It is shown that at reasonable values of the internal energy none of the hypotheses concerning ball lightning can explain the appearance of the surface forces that bring about the spherical shape of the ball lightning.