This paper is a commentary on the foundational significance of the

Clifton-Bub-Halvorson theorem characterizing quantum theory in terms of three

information-theoretic constraints (Foundations of Physics 33, 1561-1591 (2003);

quant-ph/0211089). I argue that: (1) a quantum theory is best understood as a

theory about the possibilities and impossibilities of information transfer, as

opposed to a theory about the mechanics of nonclassical waves or particles, (2)

given the information-theoretic constraints, any mechanical theory of quantum

phenomena that includes an account of the measuring instruments that reveal

these phenomena must be empirically equivalent to a quantum theory, and (3)

assuming the information-theoretic constraints are in fact satisfied in our

world, no mechanical theory of quantum phenomena that includes an account of

measurement interactions can be acceptable, and the appropriate aim of physics

at the fundamental level then becomes the representation and manipulation of

information.