 Our methods of empirical observation are unavoidably biased towards detecting conditions which are compatible with the existence of observers. For example, even if life-hostile places vastly outnumber life-friendly places in our universe, we should not be surprised to find ourselves in one of the relatively few places that are life-friendly and seek an explanation for this finding, simply because—in virtue of being living organisms—we could not possibly have found ourselves in a life-hostile place. Biases that result from the fact that what we observe must be compatible with the existence of observers are referred to as observation selection effects. The observation selection effects emphasized by the weak anthropic principle with respect to location in the universe are emphasized by what Carter dubs the strong anthropic principle (SAP) with respect to the universe as a whole: