(M222) But if on its ethical side the teaching of Empedocles may almost be described as Buddhism relieved of its deepest shadows, on its scientific side it curiously anticipated some speculations which have deeply stirred the European mind in our own and our fathers' days. For to his savage psychology and religious mysticism Empedocles superadded a comprehensive and grandiose theory of the material universe, which presents a close analogy to that of Herbert Spencer. The scientific doctrine of the conservation of energy or, as he preferred to call it, the persistence of force, which Spencer made the corner-stone of his system, has its counterpart in the Empedoclean doctrine of the conservation or indestructibility of matter, the sum of which, according to him, remains always constant, never undergoing either increase or diminution.(916) Hence all the changes that take place in the physical world, according to Empedocles, resolve themselves into the integration and disintegration of matter, the composition and decomposition of bodies, brought about by the two antagonistic forces of attraction and repulsion, which in mythical language he called love and hate. And just as all particular things are evolved by the force of attraction and dissolved by the force of repulsion, a state of concentration or aggregation in the individual perpetually alternating with a state of diffusion or segregation, so it is also with the material universe as a whole. It, too, alternately contracts and expands according as the forces of attraction and repulsion alternately prevail. For it was the opinion of Empedocles that a long, perhaps immeasurable, period of time, during which the force of attraction prevails over the force of repulsion, is succeeded by an equally long period in which the force of repulsion prevails over the force of attraction, each period lasting till, the predominant force being spent, its action is first arrested and then reversed by the opposite force; so that the material universe performs a periodic and rhythmic movement of alternate contraction and expansion, which never ceases except at the moments when, the two opposite forces exactly balancing each other, all things come to rest and equilibrium for a time, only however to return, with the backward sweep of the cosmic pendulum, to their former state either of consolidation or of dispersion. Thus under the influence of attraction and repulsion matter is constantly oscillating to and fro: at the end of a period of contraction it is gathered up in a solid globe: at the end of a period of expansion it is diffused throughout space in a state of tenuity which nowadays we might describe as gaseous. And this gigantic see-saw motion of the universe as a whole has gone on and will go on for ever and ever.(917)