Is this a good thematic statement?

I'm reading The Strange Case of Dr. Jekyll and Mr. Hyde and I need to write a thematic statement about the dual nature of man (the struggle within a person to choose good and evil)...and this is what I have so far : "The darkness automatically strikes against the light." I don't know if it's a good thematic statement..and I need help coming up with more. Best answer gets 10 points :)