at first , when any of them is liberated and compelled suddenly to stand up and turn his neck round and walk and look towards the light , he will suffer sharp pains ; the glare will distress him , and he will be unable to see the realities of which in his former state he had seen the shadows ; and then conceive someone saying to him that what he saw before was an illusion , but that now , when he is approaching nearer to being and his eye is turned towards more real existence , he has a clearer vision .