But he had early discovered that one wall of his world was different from the rest. This was the mouth of the cave and the source of light. He had discovered that it was different from the other walls long before he had any thoughts of his own, any conscious volitions. It had been an irresistible attraction before ever his eyes opened and looked upon it. The light from it had beat upon his sealed lids, and the eyes and the optic nerves had pulsated to little, sparklike flashes, warm-coloured and strangely pleasing. The life of his body, and of every fibre of his body, the life that was the very substance of his body and that was apart from his own personal life, had yearned toward this light and urged his body toward it in the same way that the cunning chemistry of a plant urges it toward the sun.