specific case of $(g-2)_\mu$, numerical work might supply an important input even while falling well short of the “fantasy” of first-principles calculation. At present the major uncertainty in the standard model prediction arises from a discrepancy between the value of the hadronic vacuum polarization as extracted extracted from $e^+e^-$ annihilation or from $\tau$ decay. Even a fairly crude numerical determination of the vacuum polarization at a single Euclidean momentum might tell us which to believe.

### Quantitative Anthropics

At the frontiers of where physics has come under control, we can start to contemplate expansion into metaphysics. Specifically, knowing the continuous parameters (in mathematicalese, moduli) of our world-theory, we can ask – and hope to answer! – a precise scientific version of the great question: Could things have been different? It seems to me that this question has taken on a new urgency due to recent developments in physics, as I have discussed at length elsewhere. There are two important refinements of the question:

-   [*Anthropic Principle*]{}: Are the values of some or all of the moduli determined by the requirement that there should be intelligent observers capable of detecting them? This could be true if the Universe were inhomogeneous on 