Making a thesis evolve

The main thing that stood out to me was that the more your paper goes on, the more your thesis evolves. so, i think that this is telling us that your thesis is just a statement about your paper that needs to be proven by your information in the body of your essay.  The more stuff that you have to prove your thesis, the better it becomes.  That is why they say it is evolving.  Another main point is that you have to work at it.  It doesnt just come to you.  I wish it would, then the paper wouldnt be so hard.  My thesis is kind of similar to the one at the end of this reading.  It stands out and can be proven, and I'd like to think that mine can too.