We are going to contrast the way Locke’s chapter on property rights is taught in philosophy classes with what an economist finds in it.
The philosophy version is that Locke is an early libertarian who is arguing for natural property rights. As far as this way of reading Locke is concerned, the chapter could pretty much end around §31 or, if you want to stretch it out, §39. (§39 really does appear to give an answer the question that was originally posed; it’s a natural place to think “he’s done now.”)
And yet Locke himself does not stop at §31 or even §39. He goes all the way to §51. Why?
What Professor Brown finds is an anticipation of distinctions that economists would develop after Locke’s time. Locke treats acorns are consumption goods (see §31), land as productive inputs (§§32–44), and money as a store of value (§45–51).
Locke was not asking the kind of questions that economists ask. He had moral commitments to the propositions that it is wrong to acquire goods and let them spoil and that it is wrong to acquire property without leaving enough and as good for others. His question was how private property could be compatible with these commitments. It was in the course of answering this fundamentally moral question that he developed these concepts that economists find so useful.
It seems to me that you can find three different moral arguments for property rights in Locke:
A natural rights story: people have natural rights to their bodies and so they acquire property rights when they labor on unowned things. Locke says, mysteriously, that they “mix” their labor with the things they come to own (§27)
A proto-utilitarian story: God commands us to promote the good of mankind and property rights accomplish that goal by giving people an incentive to make natural resources more productive (§32).
A virtue story: property rights go to the “industrious and rational” when you allocate them according to labor (§34)
While Locke thinks they all amount to the same thing, they really have different implications. A utilitarian, for instance, would be willing to take away property from someone who labored if doing so would promote the overall good.