Agni's father is, as has been said, the sky, or rather the light, the sun, the source of all warmth and life upon the earth. He bears the name of Savitar, which means "creator" or "mover," is called "the lord of creation," "the father of all life," "the living one," or "the heavenly father" simply. [177] At the same time Tvashtar also passes as the father of Agni. His name characterises him simply as modeller (world-modeller) or work-master, divine artist, skilful smith, or "carpenter," in which capacity he sharpens Brihaspati's axe, and, indeed, is himself represented with a hatchet in his hand. [178] He appears to have attained this rôle as being the discoverer of the artificial kindling of fire, by means of which any fashioning (welding), any art in the higher sense of the word became possible, as being the preparer of the apparatus for obtaining fire by friction or rotation--"the fire cradle"--which consisted of carefully chosen wood of a specified form and kind. Finally, the production of fire is ascribed to Matariçvan also, the God of the Wind identical with Vayu, because fire cannot burn without air, and it is the motion of the breeze which fans the glimmering spark. [179] All of these different figures are identical with one another, and can mutually take the place one of another, for they are all only different manifestations of warmth. It is this which reveals itself as well in the lightning of the sky and motion of the air, as in the glimmering of the fire, and not only as the principle of life, but also as that of thought and of knowledge or the "word" (Vâc, Veda), appearing on the one side as the productive, life-giving, and fructifying power of nature, on the other as the creative, inspiring spirit. This is the reason why, among the ancients, the God of life and fertility was in his essential nature a Fire-God, and why the three figures of the divine "father," "son," and "spirit," in spite of the differences of their functions, could be looked upon without inconsistency as one and the same being.