In Proudhon’s period, the animating assumption of essentially all works on property was that God created the earth and gave it to mankind in common to use. This was the long-standing Christian view, which was notably reflected in Thomist thought and even received a ringing endorsement from John Locke.
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The Christianist idea of the common ownership of all of the earth is Proudhon’s starting point.
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Perpetual Theft 

The Truth As It Changes;
Perpetual Theft
Why Property Is Theft and Why It Matters In undertaking this explanation, it is perhaps helpful to let the reader (and apparently Sumner) in on the...