Sorry but I disagree. You can have all the natural content on your website you want, but if you don't have backlinks it will not work. What is true is that if you create good quality content people will link to it and that will in effect raise the rank of your website. As an example, my wife is a photography and we created a review of rechargable batteries. Because there was no other content about this topic on the internet, the content was at times shown to people searching for the appropriate search term (GODP Batteries). Because the content was good we ended up getting a number of backlinks to the article. This in effect significantly lifted the entire site. Now if you search on google for GODP batteries, the article ranks higher than many reputable pages - (even amazon). The next step from there is take the link value from that page and pass it onto your other pages. In our case this is automatically done through all the links in the navigation which distribute the page rank to the many pages on the site. You can do it more purposefully though and have your nav links designated as no-follow and have only specific links directed to specific landing pages. This is just one example of a good strategy.
Keep in mind this is only covering backlinking. There are many other aspects to SEO, which in general are defined as on-page or off-page.
Hope this helps.