An unsatisfying theory of original thinking
An original idea is an idea you have produced that cannot be traced back to something you acquired, either through reading or conversation.
This definition creates two problems for us. Firstly, when you read lots of good books, you acquire lots of good ideas. Some or most of those ideas will be better than the ones you can come up with. Before learning about Newton's second law, you were free to conjure up any crazy theory about the relationship between force, mass and acceleration. But since acquiring Newton's idea, the train has left the station. It's highly unlikely you'll produce something better than Newton on that specific topic.
This leads to the second problem. This theory implies that our prior original thoughts, the ones we were so proud of, were produced from a poverty of acquired ideas; through not reading enough. This sucks. If original thinking requires a barren brain, you are forced to remain uninformed to be original.
With the theory as discussed above, we can say that your original ideas tend towards a horizontal asymptote as you acquire more ideas:
This theory of original thinking is extremely unsatisfying. A more satisfying theory of original thinking would be if the asymptote was located along the y-axis, which means our original ideas would tend to infinity as we acquired more ideas through treading. Something like this:
This theory is satisfying, and it encourage us to read as much as we can. The more we read, the more original we become.
I do not yet have proof of this theory. Maybe I'll read up on original thinking, and it'll come to me.