Simple and complex are relative terms.
What a highly educated person anno 2009 would find simple might be complex to a uneducated person anno 1009.<p>Which implicates this "law" is also relative, making a more useful description:
If you make something which seems complex to you, it will not work. Begin with something that is simple to you, and than evolve it in to something complex.
Summary: the law says "A complex system that works is invariably found to have evolved from a simple system that worked. The inverse proposition also appears to be true: A complex system designed from scratch never works and cannot be made to work. You have to start over, beginning with a working simple system."<p>This is obviously closely related to Richard Gabriel's "Worse is Better", and the general philosophy of starting with a simple design, and iterating under the scrutiny of users.
That "inverse proposition" is just the contrapositive: (a => b) <=> (¬b => ¬a).<p>The inverse proposition would be that if you take a simple system that works and evolve it into a complex system, the complex system will work.