As the 'ever-during peace' at the heart of all things is supposed to result from the eternal and immutable properties of the atoms, this 'endless agitation' arises out of their unceasing motion through infinite space. There are two kinds of motion,--the one tending to the renewal,--the other, to the destruction of things as they now exist. The maintenance of our whole system depends on the equilibrium of these opposing forces-- Sic aequo geritur certamine principiorum Ex infinito contractum tempore bellum[53]. There is thus seen to be not only absolute order, but also infinite change in the processes of Nature. Decay and renovation, death and life, support the existing creation in unceasing harmony. The imagination represents this process under the impressive symbol of an endless battle, in which now one side now the other gains some position, but neither, as yet, can become master of the field-- Nunc hinc nunc illic superant vitalia rerum, Et superantur item[54]. This symbol is the poetical form of the old philosophical distinction of [Greek: auxesis] and [Greek: phthora]. It is another form of the [Greek: eris] and [Greek: philia] which to the imagination of Empedocles appeared to pervade the universe. The idea of a constant battle imparts to the infinite and all-pervading movement of Nature the interest and the life of human passion on the grandest and widest sphere of action. The greatness of the thought makes each particular object in Nature pregnant with a deeper meaning, associates trivial and ordinary phenomena with a sense of imaginative wonder, and throws an august solemnity around the familiar aspects of human life. The passage in which this principle is most powerfully announced at ii. 575, etc., swells into deeper and grander tones, as the real human pathos involved in this strife of elements is made manifest. This struggle of life and decay is no mere war of abstractions: it is the daily and hourly process of existence. Birth and death are the fulfilment of this law. 'The old order changeth, yielding place to new'-- Cedit enim rerum novitate extrusa vetustas[55]. 'New nations wax strong, while the old are waning away; the generations of living things are changed within a brief space, and, like the runners in a race, pass on the torch of life'-- Augescunt aliae gentes, aliae minuuntur, Inque brevi spatio mutantur saecla animantum Et quasi cursores vitai lampada tradunt[56]. Man also must resign himself to the universal law, and accept his life not as a thing to be possessed for ever, but only to be used for a time-- Sic alid ex alio numquam desistet oriri Vitaque mancipio nulli datur, omnibus usu[57]. Under this law of universal decay and restoration, we see the rains of heaven lost in the earth, but passing into new life in the fruits from which all living things are supported--