No, nothing like that at all. Imagine opening a file in a text editor.... the editor pops up a dialog asking you what file to open... and then grabs the file you indicated. It can do this because it has access to everything, so if it gets confused, or subverted, there's zero guarantee that it will do the right thing.

Imagine instead, your text editor called the system to get a capability, which then opened the same dialog, and gave a capability (like a file handle) to the text editor for its use. If it got confused, or subverted, the only thing it could mess up would be that one file.