Previously the sensuous, concrete material of architecture was the resisting matter of gravity, which more particularly in the art of building asserted this character of heavy material in its features of burden, constraint, power to support and be supported, and even in sculpture still retained such characteristics. Heavy material encumbers because it does not possess its centre of material unity in itself, but in something else; and it seeks for this centre and strives towards it, though it retains its position through the resistance of other bodies, which become by doing so bodies of support. The principle of light is an opposite, or extreme, of that material of weight which is not as yet enclosed within its unity. Whatever else we may predicate of light it is obvious that it is absolutely devoid of weight and offers no resistance; rather it is pure identity with itself, and thereby simple self-relation, the primordial ideality, the original self of Nature. In light Nature make its start on the path of ideality or inwardness[240], and is the universal physical ego, which of course is not carried here to the point of particularity[241], nor has as yet concentrated itself within the unit of individuality and self-seclusion, yet is thereby enabled to cancel the bare objectivity and external show of heavy matter and abstract from the sensuous and spatial totality of the same[242]. From this aspect of the more _ideal_ quality of light it becomes the physical principle of the art of painting.