The illiterates of the 21st century will not be those who cannot read and write but those who cannot learn, unlearn, and relearn.
As a philosopher I see in this a wise statement. It fits like a sidecar with the insight of Socratic wisdom: before you can truly understand anything you must become aware of how little you really know.
As a web developer it strikes me as a solid practical guide. In the 21st century the tools of our ever evolving trades–strategies, tactics, best practices, programming languages, etc.–are relentlessly changing. If you can’t learn, adapt, examine, test, adjust, you will fall behind in one way or another.
Steven Covey makes a similar observation in another way in The 7 Habits–the bible of personal and professional growth:
With the dizzying rate of change in technology and increasing competition driven by the globalization of markets and technology, we must not only be educated, we must constantly re-educate and re-invent ourselves. We must develop our minds, and continually sharpen and invest in the development of our competencies to avoid becoming obsolete.