The definition of the field (gravitation field, electric field and magnetic field) implies a hypothesis: suppose there is a point field source (mass or positive charge) of one unit on the observation point P, and the magnitude and direction of the force it receives (gravitation, Coulomb force and magnetic force) is the magnitude and direction of the field strength on the point. When the field is further extended into a continuous differentiable function in space-time, the above implicit assumption is further extended as follows: there is a point field source of one unit at all spatial positions in space-time. The objective reality is that the distribution of field sources in space-time is not continuous, nor stable. As a result, many physical theories, theorems and laws based on field and field theory cannot be consistent with objective facts. Such as: electromagnetic induction law, Gauss law, Hubble law, Maxwell equations, relativity, quantum mechanics and the Big Bang theory. This article carries on some discussion and certification, hope interested friends put forward more valuable comments and suggestions.