From these high places of his philosophy,--'the "templa serena" well-bulwarked by the learning of the wise'[425] he derives not only a sense of certainty in thought and security in life, but also his wide contemplative view, and his profound feeling of the majesty of the universe. The idea of universal law enables him to apprehend in all the processes of Nature a presence which awakens reverence and enforces obedience. This idea imparts unity of tone to the whole poem, informs its language, and seems to mould the very rhythm of its verse. (2) But a closer view brings another aspect of the world into light; viz., the interdependence of all things on one another. There is not only fixed order, but there is also infinite mobility in Nature. The sum of all things remains unchanged, though all individual existences decay and perish. So too the sum of force remains the same[426]. There is no rest anywhere; all things are continually changing and passing into one another; decay and renovation form the very life and being of all things. Nothing is ever lost. 'Nature repairs one thing from another, and allows of no birth except through the death of something else':-- Haud igitur penitus pereunt quaecumque videntur, Quando alid ex alio reficit natura nec ullam Rem gigni patitur nisi morte adiuta aliena?[427] 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.[428] 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.[429]