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He concluded by telling the crowd that he couldn’t continue teaching in a traditional setting. “Having done this, I can’t teach at Stanford again,” he said.

One of Udacity’s first offerings will be a seven-week course called “Building a Search Engine.” It will be taught by David Evans, an associate professor of computer science at the University of Virginia and a Udacity partner. Mr. Thrun said it is designed to teach students with no prior programming experience how to build a search engine like Google. He hopes 500,000 students will enroll.

Teaching the course at Stanford, Mr. Thrun said, showed him the potential of digital education, which turned out to be a drug that he could not ignore.

“I feel like there’s a red pill and a blue pill,” he said. “And you can take the blue pill and go back to your classroom and lecture your 20 students. But I’ve taken the red pill, and I’ve seen Wonderland.”