## Abstract

In recent articles by this author, [
S. Karp,
Statistical properties of ensembles of classical wave packets,
J. Opt. Soc. Am. **65**,
421 (
1975);
S. Karp,
Test for the nonexistence of photons,
J. Opt. Soc. Am. **66**,
1421 (
1976)], a radiation model was proposed that could lead to the identification of certain classical properties of the field, based upon photoelectric counting experiments. Mandel [
L. Mandel,
Photoelectric counting measurements as a test for the existence of photons,
J. Opt. Soc. Am. **67**,
1101 (
1977)] responded by asserting that “It follows that for any field for which a classical wave description exists, in the sense that the phase-space density *ϕ*({*ν*}), and therefore *P*(*u*), are non-negative it is impossible to distinguish between photons and light waves in photoelectric counting experiments.” This statement is based upon the derivation of similar photoelectron counting equations using quantum and classical techniques. It is the mathematically loose associations and subsequent rigid physical interpretation implied in relating the two equations that is under contention. It seems to us that the model-computation-effect approach to physics is still solvent. In particular, if we can model an effect as small as the radiation from an individual electron and produce a predictable effect, then the physics underlying the model must be seriously considered.

© 1979 Optical Society of America

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