He was the guy who thought that people were too dumb to operate a two-button mouse.
Did he say this, or are you inferring it from his having designed a one-button mouse?
Having two incorrect beliefs that counter each other (thinking that people want to spend time on your creation but are less intelligent than they actually are) could result in good designs, but so could making neither mistake. I'd expect any decent UI designer to understand that the user shouldn't need to pay attention to the design, and/or that users will sometimes be tired, impatient or distracted even if they're not stupid.
Did he say this, or are you inferring it from his having designed a one-button mouse?
I recall reading that he tried 3 button mouse, didn't like it, said it was too complicated, and gone for an one button one. Further down the road they need the difficult-to-teach alternate-click functionality and implemented it with option-click rather than an extra button. Apple stuck with one button mouse until 2005 or so, when it jumped to 4 programmable buttons and a scrollball.
The inventor of the mouse and of many aspects of the user interface, Douglas Engelbart, gone for 3 buttons and is reported on wikipedia as stating he'd put 5 if he had enough space for the switches.
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