Not knowing this difference means you might apply exactly the wrong approach to the right problem. (Or, if you prefer, the right approach to the wrong problem.)
It's a simple message, really. But if you don't get it, you're headed for chaos.
Simple = easily knowable.
Complicated = not simple, but still knowable.
Complex = not fully knowable, but reasonably predictable.
Chaotic = neither knowable nor predictable.
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