Symbols can confirm or clarify themes by using something but it meaning something else that reveal the theme, for example, the theme is kindness is often overshined by greed, the symbol is a caged bird without food in a magic castle trapping a selfish, greedy prince. It is only when the prince gets board of the castle but can't go outside because of the magic spell, and realizes the bird also wants freedom, that the theme shows, or is revealed.
