  Prediction in quantum cosmology requires a specification of the universe's
quantum dynamics and its quantum state. We expect only a few general features
of the universe to be predicted with probabilities near unity conditioned on
the dynamics and quantum state alone. Most useful predictions are of
conditional probabilities that assume additional information beyond the
dynamics and quantum state. Anthropic reasoning utilizes probabilities
conditioned on `us'. This paper discusses the utility, limitations, and
theoretical uncertainty involved in using such probabilities. The predictions
resulting from various levels of ignorance of the quantum state are discussed
including those related to uncertainty in the vacuum of string theory. Some
obstacles to using anthropic reasoning to determine this vacuum are described.
