Douglas Engelbart, a technologist who conceived of the computer mouse and laid out a vision of an Internet decades before others brought those ideas to the mass market, died on Tuesday night. He was 88.

His eldest daughter, Gerda, said by telephone that her father died of kidney failure.

Engelbart arrived at his crowning moment relatively early in his career, on a winter afternoon in 1968, when he delivered an hour-long presentation containing so many far-reaching ideas that it would be referred to decades later as the "mother of all demos".

Speaking before an audience of 1,000 leading technologists in San Francisco, Engelbart, a computer scientist at the Stanford Research Institute (SRI), showed off a cubic device with two rolling discs called an "X-Y position indicator for a display system". It was the mouse's public debut.

Engelbart then summoned, in real-time, the image and voice of a colleague 48 km away. That was the first videoconference. And he explained a theory of how pages of information could be tied together using text-based links, an idea that would later form the bedrock of the Web's architecture.

At a time when computing was largely pursued by government researchers or hobbyists with a countercultural bent, Engelbart never sought or enjoyed the explosive wealth that would later become synonymous with Silicon Valley success. For instance, he never received any royalties for the mouse, which SRI patented and later licensed to Apple.

He was intensely driven instead by a belief that computers could be used to augment human intellect. In talks and papers, he described with zeal and bravado a vision of a society in which groups of highly productive workers would spend many hours a day collectively manipulating information on shared computers.

"The possibilities we are pursuing involve an integrated man-machine working relationship, where close, continuous interaction with a computer avails the human of radically changed information-handling and -portrayal skills," he wrote in a 1961 research proposal at SRI.

His work, he argued with typical conviction, "competes in social significance with research toward harnessing

thermonuclear power, exploring outer space, or conquering cancer."

He is survived by Karen O'Leary Engelbart, his second wife, and four children: Gerda, Diana, Christina and Norman. His first wife, Ballard, died in 1997.