U.S. Supreme Court Justice Potter Stewart famously said of pornography that he couldn’t define it, “but I know it when I see it.”

One might very well say the same thing about entrepreneurship. We all encounter entrepreneurs in our work. We recognize them when we see them. But when pressed for a definition, we might find it difficult to come up with a concise answer. What makes an organization entrepreneurial? What are the distinguishing characteristics of an entrepreneur? Is entrepreneurship a trait people are born with, or can it be taught and learned? A survey of STERNbusiness’ diverse readership would undoubtedly yield dozens of answers.

Of course, in today’s economy, when no market leader’s status is secure and competition can rise from myriad sources, the ability to act like an entrepreneur is crucial to survival – whether you’re a car manufacturer or a university. Indeed, in the lead article of this issue, Professor Ari Ginsberg, director of NYU Stern’s Berkley Center for Entrepreneurial Studies, examines how managers in larger, mature corporations have focused on the important role of entrepreneurship in creating opportunities for corporate growth and renewal (p. 12). In fact, Ginsberg notes, all sorts of firms are using “corporate venturing” to leverage their assets and capabilities and create new businesses.

Of course, classic entrepreneurs are individuals who start businesses from scratch, or take tiny enterprises and grow them into something much, much larger. That’s why the trio of successful entrepreneurs whose appearances at Stern are chronicled in this issue are particularly appropriate. Taken together, the words of these three CEOs constitute a sort of first-person manual on how to start, grow, and re-start businesses. And there are some valuable lessons to be learned from their experience.

An often overlooked component of entrepreneurship is knowing when to sell. That frequently excruciating decision, after all, can often mean the difference between survival and extinction. Kenneth Cron (p. 2), who led the Uproar Network, an Internet-entertainment start-up, through the dot-com shakeout, recognized the necessity of joining up with a larger outfit and engineered the sale of his company to Vivendi. While many of its independent rivals have been relegated to the dot-com dustbin, Uproar is still alive and well.

The essence of entrepreneurship is seeing an opportunity where others do not and making the most of your resources. In 1994, upscale urban coffee shops were popping up like wildflowers after a spring rain. But Andrew Stenzler (p. 6), who received his Stern MBA that year, saw a niche. He founded Xando, Inc., which combined the coffee house concept with a neighborhood bar. “Most restaurants get three usages out of their real estate, i.e. breakfast, lunch and dinner,” he said. “We get five full day parts.” The company, since renamed Xando Cosí, now has an impressive 55 outlets.

What else defines an entrepreneur? How about resilience? J. Peterman, co-founder and former CEO of J. Peterman Company, was rejected by 100 venture capitalists before an advertisement in The New Yorker helped coax an investor to fund his catalog of off-beat products. The rest is history: the company grew rapidly, Peterman evolved into a cult hero, and the firm ran into troubles and went bankrupt. But Peterman himself was undeterred by the failure. “I’m presented with another opportunity in life,” he says. Peterman took some time off, worked on a book – Peterman Rides Again – and, naturally, has started a new company.

There’s also much to be learned by studying those who wrote and thought about entrepreneurship. Take Pulitzer-prize-winning historian Thomas McCraw’s profile of the leading theorist of entrepreneurship – Joseph Schumpeter (p. 18). Although he died a half-century ago, Schumpeter is enjoying something of a present-day vogue. After all, he coined the term “Creative Destruction,” a buzzword of the New Economy. But the economist’s legacy was far greater than a few catchy terms, McCraw argues. Schumpeter delved into history, sociology, and psychology to make penetrating observations on the workings, motivations, and effects of entrepreneurs.

In their article, Anthony Afuah and Christopher Tucci put some of Schumpeter’s theory into practice (p. 24). The authors wondered exactly how one of the great vehicles for entrepreneurship – the Internet – acts as a force of creative destruction. They constructed a theoretical model, which they then applied to three broad industry groups, defined by the ways in which they use technology. Their conclusions may prove valuable to managers and executives.

The relationship between patents and entrepreneurs has always been complicated. Patents, after all, have long provided inventors and innovators a way to protect their new products from imitation. On the other hand, patents have also been wielded by their holders as a blunt instrument in warding off potential competition. In the Internet economy, patents covering business models have emerged as a topic of great controversy and litigation: think Priceline.com’s shopping system or Amazon.com’s one-click ordering method. William Greene provides some valuable perspective on the history of business-method patents (p. 30).

Aside from the United States Patent and Trademark Office, there’s another government agency that has occasionally proved something of a challenge to entrepreneurs: the Federal Communications Commission. Among other responsibilities, the FCC manages the airwaves, which have been a platform for entrepreneurship dating back to the first radio stations in the 1920s. And analysts are placing great store in the publicly-managed spectrum as the host to wireless and other next-generation Internet applications. But Lawrence White (p. 42) argues that the FCC’s spectrum management philosophy, rooted in thinking that may have made sense in the 1920s, is outdated and serves to stifle entrepreneurship and innovation. White proposes a radical, but logical alternative: regulators should think of the airwaves as another form of real estate, and enact a regulatory regime similar to that which governs the use of property in this country.

It’s precisely this sort of entrepreneurial thinking that makes this issue of STERNbusiness an enjoyable, interesting, and useful read.

Daniel Gross is editor of STERNbusiness.