Five years ago, at the height of the Internet boom, Martin Gagen drew a plum assignment when he was asked to open the Silicon Valley office of private equity giant 3i Group. Gagen, who had previously run the London-based firm's buyout business, set up shops in Menlo Park, California, and, later, Waltham, Massachusetts -- offices that now employ 30 people -- and oversaw $600 million of investments in 80 companies. But technology and venture capital have lost a lot of the old excitement -- and so, for Gagen, did 3i.

He left the firm in August and last month entered a master's program in philosophy and history at Stanford University. Gagen, 47, says the academic life is now his "one absolute objective." He has an undergraduate degree in political science from the U.K.'s University of Hull, and he attended the advanced management program at France's Insead; ultimately, he wants to earn a Ph.D. and teach. "I have a very strong desire to educate bright, motivated students in history and cultural philosophy," says Gagen, who is divorced and has two children who are attending British universities.

It's a radical departure, to say the least. Gagen notes that over 18 years with 3i -- his entire career, except for a three-year stint in the late 1980s with Investcorp in New York -- he launched the firm's U.S. and Asia-Pacific operations and filled "all the top jobs but CEO." Some expected him to become CEO in July when Brian Larcombe, 50, retired, but he declined to run, and former Investcorp and Diageo executive Philip Yea got the post. "I wanted a clean break from 3i," asserts Gagen. But not a complete break from wheeling and dealing: He reckons that after six to 12 months of concentrated study, he'll be ready to devote about 40 percent of his time to business dealings, especially with U.S. companies that have operations in China. "I have a very open mind," he says, "and this could lead me in very unexpected directions."