In advertising, you don’t get much bigger than Procter & Gamble — or much smaller than a start-up with your name on the door. But it seems Jim Stengel, the former P&G global marketing head, figures he can make something big out of the small company he’s launching on Monday, Jim Stengel LLC.

Indeed, in the release announcing the new venture, which wasn’t a very well-kept secret, he says the goal of the company is “to accelerate a movement to deeply rethink and transform the roles and meaning of marketing and branding.”

Now that’s big.

Basically, Stengel’s philosophy is that marketing should be purpose-based, meaning advertising should address the fundamental question of how a company helps make a customer’s life better.

Or as the Wall Street Journal put it earlier this week: The well-known adman maintains that the idea of “purpose” isn’t just the latest cooked-up marketing-speak. He says dozens of companies and brands have used this approach. He points to P&G’s Pampers brand, which several years ago decided it had a higher purpose: helping moms develop healthy, happy babies, rather than just keeping babies’ bottoms dry.

So how does Stengel get the rest of the advertising world on board? He says he’s going to write a book, consult with business leaders, and land some speaking engagements. It’s a little different than pitching Pampers, Head & Shoulders, or Tide, but you never know…