Actually to have a higher PR you are supposed to get backlinks. However if your site is new and the content is great, most of the bloggers will automatically link to your site and you will get a backlink. But in order to get such links, you need to have a great content site
you can.. just dont expect it to be high.. I had a site get a PR 1 when there were no links to it, and no links from that site to anywhere else..
Yes, technically you can get PR without any inbound links from other sites. Every page in a website receives some unknown, but very small value, once G crawls it. That page can then pass up to 85% of its value to one or more other pages. So if every page in your site linked back to your home page, and if you had one million of these internal pages, your home page would get a nice PR value. Again, that is all theoretical. Every page would need to be of high quailty or G might not count it. And of course a large site with quality content would receive lots of natural BLs. So, it is not realistic, but theoretically possible. There is an old, but very good explanation of how PR works with internal pages here: http://www.webworkshop.net/pagerank.html#internal_linking