‘The similes of the Sun, Line, and Cave in the Republic remain a reproach to Platonic scholarship because there is no agreement about them, though they are meant to illustrate.’ So wrote A.S. Ferguson in 1934, and so he could write to-day. Four decades have produced at least twenty more substantial contributions to the debate, but no agreement. I shall not attempt to arbitrate between existing interpretations, nor shall I offer an account of the ‘simile of light’ as a whole. I shall confine my attention to a single point: the significance of the shadows in the cave, and of the objects which cast them. The suggestion I shall make seems an obvious one, but I have not found it in the literature. I hope to show at least that it deserves serious consideration.