Different people have different memories and emphasis of how the Macintosh was developed, and where the underlying ideas originated. While the connection between the Macintosh and the Alto project at Xerox PARC has been firmly established in the historical record, the earlier contributions of [Ivan Sutherland]?'s Sketchpad? and Doug Engelbart's [On-Line System]? are no less significant. See History of the GUI.
/History of the Mac OS
See OS Advocacy.