  Two results support the idea that the scalar and vector potentials in the
Lorenz gauge can be considered to be physical quantities: (i) they separately
satisfy the properties of causality and propagation at the speed of light and
not imply spurious terms and (ii) they can naturally be written in a manifestly
covariant form. In this paper we introduce expressions for the Lorenz-gauge
potentials at the present time in terms of electric and magnetic fields at the
retarded time. These expressions provide a third result in favor of a physical
interpretation of the Lorenz-gauge potentials: (iii) they can be regarded as
causal effects of the observed electric and magnetic fields.
