Once extracted from the ground, materials like petroleum, coal, and minerals are not replaced or readily renewed, at least not on a time scale that is directly relevant to humans. They are nonrenewable resources, bearing in mind that “resources” might not be the most appropriate appellation, or rather, its appropriateness might occlude a dimension of resources that cannot be appropriated or turned into property. In contrast to nonrenewable resources, renewable resources can be used indefinitely. Consider resources like wind, sunlight, flood control, and ideas. If a windmill absorbs energy from the wind, more wind is on the way, becoming renewed as the heat from the sun is continually generating differences in atmospheric pressure around the surface of Earth. If sunlight is used by photosynthesizing plants or solar panels, more sunlight is on the way, for the next five billion years or so, until the sun begins dying. If you rely on flood control provided by a forest, you are not subtracting from the flood control that the forest provides for others. If you learn an idea, you do not thereby deplete the idea or limit the access that others have to the idea.