Suppose I sell some of my wool to you in exchange for some of your sparkling pebbles. The deal, if freely agreed upon, satisfies us both. Ideally, this is how the free market works. A laissez-faire economic system assumes that the interplay of self-interested individuals and entities in the marketplace will result in maximal gains for both producers and consumers and that this interplay should be, for the most part, free of government intervention. But what if a freely negotiated deal ends up causing harm to people who were not part of the deal? Suppose my wool-production pollutes the stream that runs down into my neighbor's property? Suppose your pebble-sparkler gives off toxic emissions that cause nearby children to develop asthma? These are examples of "negative externalities," cost that free markets sometimes impose on people who have not consented to them, and who are not compensated for them. Locke, writing before the Industrial Revolution, does not address them. Are there other ways in which Locke's philosophy does not appear to fit the twenty-first-century context?