  Path integrals represent a powerful route to quantization: they calculate
probabilities by summing over classical configurations of variables such as
fields, assigning each configuration a phase equal to the action of that
configuration. This paper defines a universal path integral, which sums over
all computable structures. This path integral contains as sub-integrals all
possible computable path integrals, including those of field theory, the
standard model of elementary particles, discrete models of quantum gravity,
string theory, etc. The universal path integral possesses a well-defined
measure that guarantees its finiteness, together with a method for extracting
probabilities for observable quantities. The universal path integral supports a
quantum theory of the universe in which the world that we see around us arises
out of the interference between all computable structures.
