The Gods, when they undertook the fabrication of the body, foresaw the inconvenience of allowing the head--with its intelligent rotations, and with the immortal soul enclosed in it--to roll along the ground, unable to get over a height, or out of a hollow.[58] Accordingly they mounted it upon a tall body; with arms and legs as instruments of movement, support, and defence. They caused the movements to be generally directed forward and not backward; since front is more honourable and more commanding than rear. For the same reason, they placed the face, with the organs of sense, in the fore part of the head. Within the eyes, they planted that variety of fire which does not burn, but is called light, homogeneous with the light without. We are enabled to see in the daytime, because the light within our eyes pours out through the centre of them, and commingles with the light without. The two, being thus confounded together, transmit movements from every object which they touch, through the eye inward to the soul; and thus bring about the sensation of sight. At night no vision takes place: because the light from the interior of our eyes, even when it still comes out, finds no cognate light in the air without, and thus becomes extinguished in the darkness. All the light within the eye would thus have been lost, if the Gods had not provided a protection: they contrived the eyelids which drop and shut up the interior light within. This light, being prevented from egress, diffuses itself throughout the interior system, and tranquillises the movements within so as to bring on sleep: without dreams, if all the movements are quenched--with dreams, corresponding to the movements which remain if there are any such.[59] [Footnote 58: Plato, Timæus, p. 44 D-E. [Greek: i(/n' ou)=n mê\ kulindou/menon e)pi\ gê=s, u(/lê te kai\ ba/thê pantodapa\ e)chou/sês, a)poroi= ta\ me\n u(perbai/nein, e)/nthen de\ e)kbai/nein, o)/chêm' au)tô=| tou=to kai\ eu)pori/an e)/dosan.]] [Footnote 59: Plato, Timæus, p. 45. The theory of vision here given by Plato is interesting. A theory, similar in the main, had been propounded by Empedoklês before him. Aristotel. De Sensu, p. 437 b.; Theophrast. De Sensu, cap. 5-9, p. 88 of Philipson's [Greek: U(/lê A)nthrôpi/nê]. Aristotle himself impugns the theory. It is reported and discussed in Galen, De Hippocratis et Platonis Dogmat. vii. 5, 6, p. 619 seqq. ed. Kühn.