Recently Tomonaga and Schwinger have independently developed a covariant formulation of quantumelectrodynamics (super-many-time theory), and have successfully applied it to the explanation of the Lamb shift in the hydrogen atom and the anomalous magnetic moment of the electron. They have shown that, although the present theory of fields, in general, gives infinte answers to such field reaction problems, since it cannot be formulated in a Lorentz- and gauge-covariant way without introduction of the singular delta function of Jordan and Pauli, it is nevertheless possible to avaid the divergences by amalgamating them into the mass and charge, and that the remaining finite term can well account for the experimental facts. But there remains the question, whether or not such finite term, as is separated from infinity, can be free from any ambiguity arising from the pathological character of delta function of Jordan and Pauli. One typical example of the appearance of such an ambiguity is the photon self energy. As first pointed out by Schwinger, the photon self energy should be zero from the gauge covariant point of view, while, completely against Schwinger's prediction, the recent calculation by Wentzel leads to a finite but non-gauge covariant result for the photon self energy. It is evident that this inconsistent result comes from the mathematical difficulty of obtaining a definite expression for the singularity of the light cone of Jordan-Pauli's delta function. A very similar situation is also encountered in the γ decay of neutral meson. By using the method of evaluation which has been applied by Schwinger to the calculation of the anomalous magnetic moment of the electron, we have obtained the convergent but non-gauge covariant result for the γ decay of neutral meson. Further our result is inconsistent with the recent discussions of Dyson, Sawada and Nanbu on the equivalence between the pseudoscalar and pseudovector couplings of the pseudoscalar meson field. Thus, in the present state of the field theory, we cannot give an unambiguous life-time for neutral meson. It is very desirable to find some general prescription which enables one to get the definite answer to field reaction problams.