Theory of Ideas!!

Idea!

Lately I have been wondering about where do the ideas/thoughts come from! though I know whatever I think I can't be sure of it ! :p

1) Many a times it so happens that what we think as "our idea" , upon researching we find that someone has already "thought" about it earlier . So how can we be sure that the ideas that we are having are ours in the first place?

2) Newton had an idea/theory about gravity! Einstein came and changed the ways we think about it.An idea can be true for a generation but maynot be true for all generations! Are ideas relative?

3) Most Ideas are tweaked versions of earlier ideas! First person who thought of "currency" was he "original thinker". My contention is he was not the first one who was grappling with the problems arising in barter system as size of the society was increasing! He was not the first one who was grappling with the problem of defining the worth of a commodity or service.

5) What gives us ideas in most of the situations is a "Goal" , a "purpose". Then its just the matter of persistance with that goal with that purpose and you'll get the so called ideas. It reminds me of the mythological tree "kalpvraksh" which my mum used to tell me about when I was a kid.
The similarity, between the kalpvraksh and the ideas, that we get after persisting with the goal, is you get what you want! Though in our case,of ideas, result is not instantaneous! But then I am not sure if mum ever told me that if it was instantaneous in Kalvraksh's case either.