a market and tends to use the consumer's choices as evidence (revealed preference) that various products are of economic value. In this view, religious or political struggle over what "goods" are available in the marketplace is inevitable, and consensus on some core questions about body and society and ecosystems affected by the transaction, are outside the market's goods so long as they are unowned. However, some natural goods seem to also be moral goods. For example, those things that are owned by a person may be said to be natural goods, but over which a particular individual(s) may have moral claims. So it is necessary to make another distinction: between moral and non-moral goods. A non-moral good is something that is desirable for someone or other; despite the name to the contrary, it may include moral goods. A moral good is anything which an actor is considered to be morally obligated to strive toward. When discussing non-moral goods, one may make a useful distinction between inherently serviced and material goods in the marketplace (or its exchange value), versus perceived intrinsic and experiential goods to the buyer. A strict service economy model takes pains to distinguish between the goods and service guarantees to the market, and that of the service and experience to the consumer. Sometimes, moral and natural goods can conflict. The value of natural "goods" is challenged by such issues as addiction. The issue of addiction also brings up the distinction between economic and moral goods, where an economic good is whatever stimulates economic growth. For instance, some claim that cigarettes are a "good" in the economic sense, as their production can employ tobacco growers and doctors who treat lung cancer. Many people would agree that cigarette smoking is not morally "good", nor naturally "good," but still recognize that it is economically good, which means, it has exchange value, even though it may have a negative public good or even be bad for a person's body (not the same as "bad for the person" necessarily – consider the issue of suicide). In ecological economics value theory is separated into two types: donor-type value and receiver-type value. Ecological economists tend to believe that 'real wealth' needs a donor-determined value as a measure of what things were needed to make an item or generate a service (H. T. Odum, Environmental Accounting: Emergy and environmental decision-making, 1996). An example of receiver-type value