If you have an apple and I have an apple and we exchange apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas.
Context / explanation
Ideas shape the course of history.John Maynard Keynes
A good idea, only be sure to make a copy of everything before getting rid of it.Samuel Goldwyn
Great minds discuss ideas. Average minds discuss events. Small minds discuss people.Eleanor Roosevelt
An invasion of armies can be resisted, but not an idea whose time has come.Victor Hugo
A person with a new idea is a crank until the idea succeeds.Mark Twain