On Frege's True And False Thoughts

In Frege's view,truth cannot defined,thus the problem of logical truth cannot be solved by defining truth once and for all.Following the basic way from thought to truth,Frege thinks that the primary task of logic research is not to define truth,but to determine the scope of application of truth,thought is the true scope of application.which is also the core of Frege's theory by using the other way.Although Frege focuses on thought in his works,it essentially revolves around “truth”.It can be said that the basic way of Frege's logic research is from thought to truth,that is truth can be grasped with the help of thought.However,Frege also believes that thought can distinguish between false thought and true thought,so what is the relationship between false thought and true thought?Can false thought also graspe the truth?At the same time,how should we evaluate the definition and judgment of the true and false thoughts,and what kind of influence and enlightment does this theory have on modern logic?...