Thermodynamics are incoherent. Even a fundamental gas state equation has been argued for decades - , let alone to derive a consistent and simple equation to predict the thermodynamic properties of substances. The reasons are summarized as follows. Methodologically, the research depended on intuition and the method of stimulation responses. For example, the gas system has not been detected as a pure gas or gas-liquid coexisting system. The results of system responses are summarized to form the empirical formula. However, the mechanism of system response is rarely a concern. The next is the unclear definition of concepts. Newton proposed the universal gravitation, but even he doubted -"That one body may act upon another at a distance through a vacuum without the mediation of anything else, by and through which their action and force may be conveyed from one another, is to me so great an absurdity that, I believe, no man who has in philosophic matters a competent faculty of thinking could ever fall into it." Heat is another unclear concept in thermodynamics. It is described as "heat is the thermal energy transferred between systems due to a temperature difference" . Thermal energy is the kinetic energy of vibrating and colliding atoms in a substance. However, the mechanism of heat transfer is not clear. It results in the structure defects of thermodynamic theorems. For example, in the definitions of internal energy, 𝑑𝑈 = 𝛿𝑄 -𝛿𝑊 (2) U is the internal energy, and Q and W are the heat and work. In Eq. 1, the exact differential term (dU) is mixed with two inexact differential terms (δQ and δW). In mathematics, it is not compatible.