It seems to me that materialism and over-consumption can be partially explained by the idea of "the tragedy of the commons." Tragedy of the commons is an idea generally employed to justify private property. The usual example begins with a sheep pasture held in common by a group of shepherds. (Technically what we are talking about here is not common property but "open access" property -- that is, property that belongs to no one. Use of common property, a form of ownership ignored by the classic "tragedy" theory, is regulated by an authority such as the government, traditional leadership, or cultural norms.) Each shepherd will want to graze as many sheep as he can, as his income depends on them. All the shepherds keep adding sheep to their flocks, and eventually the pasture becomes degraded. None of the shepherds will voluntarily limit the size of his flock, because if one of his sheep doesn't eat a patch of grass, one of the other shepherds will find a sheep to eat it. Grabbing for the largest share ultimately destroys the shepherds' resource base. However, this doesn't happen if each shepherd has his own private pasture. He can limit the size of his flock, thus avoiding overgrazing, because he knows that any grass his sheep don't eat won't be snapped up by his neighbor. Private property encourages conservation, because it allows the benefits of conservation to accrue to the conserver.

Now, let's think about the market for wool (as an analogy to any market characterized by overconsumption). The demand of the population for wool is in a sense a resource to be used by all the shepherds. They're raising money from it by selling wool products, just like they raise wool from the pasture by having the sheep eat grass. And that resource is held in common (open access, technically) -- no shepherd has a private set of consumers that only he may sell to. So each of the shepherds will try to use as much of the demand for wool as he can.

One aspect of the problem that the usual explanation of tragedy of the commons doesn't address is the two ways in which users of a common resource try to extract more from it: the expansive strategy and the intensive strategy. The extensive strategy involves users pressing against each other. Extensive pressure doesn't lead to degradation of the resource, it merely shifts what proportion of the land is being grazed by each flock. There are still the same number of sheep per acre. In the market context, extensive competition is what companies are doing when they're trying to capture a larger market share. Each shepherd knows that any money he doesn't earn through selling his product will be earned by some other salesman. He will, of course, push against his competitors to get more out of the market, and it's the beneficial consequences of this competition that explain why capitalist theory can advocate holding markets in common when all other resources are to be privatized.

Then there's intensive pressure. The shepherd will also press harder on the share of the resource he controls. In the grazing example, imagine sheep normally bite grass off an inch above the ground, and that that level of grazing is sustainable. If that's all the harder that one shepherd is grazing the part of the pasture he's using, it leaves an inch of grass behind that another shepherd can come along and use. So each shepherd is motivated to use every scrap of grass his sheep can scrounge up. In the market context, this means driving consumers to spend more. Sellers can exercise a considerable amount of influence in creating a culture of consumption, using advertsising and other strategies to encourage people to spend more. It would be too cutesy to say here that the consumer is thus degraded. From the resource user's perspective (which is how we determined degradation in the case of the pasture), the market's productivity isn't decreasing (at least as far as I can tell, although I'm not an economist). It does, however, create a phenomenon that's widely viewed as negative from another perspective.