We are therefore forced to conclude: either that the universe began its activity at a given moment of time and will end in a similar fashion, but the beginning of activity is absurd; if a state of equilibrium had been reached it would have persisted to all eternity; Or there is no such thing as an endless number of changes, but a circle consisting of a definite number of them which continually recurs: activity is eternal, the number of the products and states of energy is limited.