 To illustrate the distinction, consider a category such as animal sacrifice. This is a kind of ritual act performed in both historical and contemporary cultures. The boundaries of this category are not simple. Animal sacrifice is not the same as ritual slaughter, though the two acts have many properties in common: the animals killed in both may be eaten, both acts may be performed by specially qualified individuals, and both may be subject to specific rules and performed in specific contexts. The first inquiry into the nature of animal sacrifice, then, is to clarify the conditions for something to be in the category: what are the essential properties of an animal sacrifice, or the constituents of an animal sacrifice?