Since its conception, the Anthropic Principle (AP) has been controversial. For some of its advocates, it replaces the Cosmological Principle and also marks a revolution in the accepted modes of scientific explanation. For critics, it is but a truism or tautology. Of course, the AP comes in various forms, ranging from plausible-sounding “weak” ones (WAP) to speculative “strong” ones (SAP) and even more speculative extreme versions. I shall survey, comment and expand on, already extant analyses of the value and use of APs, in its less speculative versions; I shall also compare the possible role of the AP with that of the principle of natural selection (PNS).
In particular, I shall argue the following points. (1) The AP is neither a constitutive nor a framework principle of scientific theories. (2) The fact that the WAP, in the sense of a “self-selection” principle (or a warning against observational bias), can be given a Bayesian formulation shows only its role as a useful piece of methodological advice. (3) This implies that WAP-arguments can undermine claims, rule out or weaken hypotheses. (4) Unlike the PNS, the WAP is not a tautology, but a self-evident statement. (5) The WAP never is a substantial premise in AP-arguments or “AP-explanations”; it can at best heuristically guide one to employ arguments in its spirit. (6) In general, WAP-arguments cannot explain events or traits of the universe; they can reduce possible amazement concerning them. (7) While the PNS indicates how to construct equally tautological, though explanatory, models of evolutionary mechanisms, the APs are too unspecific to circumscribe any such set of models; AP-arguments borrow all explanatory accounts from elsewhere. (8) The SAP, when conjoined with one of the “many worlds”-hypotheses and their explanatory power, can indeed yield (highly speculative) explanations. (9) One kind of “AP-predictions” cannot derive any predictive power from the AP; another kind consists of meta-predictions about the future course of scientific theories; certain predictions using the SAP or even stronger principles and claimed to be testable are utterly speculative. (10) While the advocacy of the AP is “locally” restricted to a particular selection of cosmologists and astrophysicists, the scientific norms and standards in terms of which they endeavour to defend the principle are “non-local”, generally accepted, if generously interpreted, ones. In their light, the employment of the AP appears-even to some of its advocates-as a temporary stop-gap.