"[The legislation] would change U.S. patent rules by giving a patent to the first person to file for it, not the first person to create a new invention." Can a

"[The legislation] would change U.S. patent rules by giving a patent to the first person to file for it, not the first person to create a new invention." Can anyone explain how this relates to prior art? If you're filing a patent for something that you're not the first person to invent, then isn't there inherently going to be prior art related to your patent, rendering it not new and non-obvious?