The contrast between consumerism and simple living at first glance seems fairly straightforward: Consumerism is about having more stuff, simple living is about having less stuff. Consumerism seems to be a permutation of the age-old vice of avarice, whose "special malice," says the Catholic Encyclopedia, "lies in that it makes the getting and keeping of money, possessions, and the like a purpose in itself to live for." As the old vitamin commercial from the 80s so bluntly put it, "I want MORE for ME."
Avarice, however, does not really exhaust the phenomenon of consumerism. Consumerism is not so much about having more as it is about having something else. It is not buying but shopping that captures the spirit of consumerism. Buying is certainly an important part of consumerism, but buying brings a temporary halt to the restlessness that typifies it. It is this restlessnessthe moving on to shopping for something else no matter what one has just purchasedthat sets the spiritual tone for consumerism.
In the Christian tradition we are accustomed to thinking that the greatest temptation associated with material things is an inordinate attachment to them. Since biblical times and before, some people have accumulated great stores of wealth, and the Bible is often quite severe in its judgment of them. When we hear that the "love of money is a root of all kinds of evil" (1 Timothy 6:10), and that the "poor in spirit" are blessed (Matthew 5:3), we resolve to cultivate an attitude of detachment from the material things we have. The problem is that consumerism is already a spiritual discipline of detachment, though one with a very different way of operating than classical Christian asceticism.