We sat down with former Ogilvy & Mather CEO Ken Roman recently to ask him about his tenure there. A full feature will run from that interview as part of MediaBistro’s So What Do You Do? series, later this month. Here is an excerpt from the interview on the subject of what makes a big idea. (Note: this is not from the WSJ’s Creative Leaders series, which we have been posting bits and pieces of under the “Back to Basics” headline. But because Mr. Roman was full of nuggets of wisdom, we felt it appropriate to include his words here)

Mr. Roman: The most important thing about a big idea beyond the fact that it is successful in building business over a period of time is that it lasts a long time. Ogilvy says a big idea has to last 20 years or more before you’re going to consider it a really big idea. Somebody who has a great commercial or a print campaign that lasts a year or two and earns money, that’s a good idea. And you’ll take it every time.

But a big idea is, well, Dove. It’ what, 40 years, 50 years old now? That’s an incredible length of time. To have an idea that’s so big that you can add line extensions, new products all under the umbrella of Dove. So it’s not a limiting idea.

Matt: All because 25% of Dove contains lotion?

Mr. Roman: That’s right, one-quarter cleansing cream. Doesn’t dry your skin the way soap does.

More: “Back to Basics: Wisdom From Allan Beaver”