With the advent of the theory of special relativity, in which the concepts of absolute time and absolute space are discarded, and general relativity, which is accompanied by an empirical interpretation of geometry and attention to non-Euclidean geometry, some basic elements in Kant's firs t critique, including the concepts of time and absolute space and the certainty of Euclidean geometry was shaken, and this provoked different reactions. For Cassirer, Eins tein's theory of relativity appears to be fruitful in three aspects. A) Eins tein's theory of relativity as a confirmation for his general epis temology; b) protecting Kant's epis temological principles agains t conflicts; c) applying the principle of relativity to the critique of knowledge and preparing the project of the philosophy of symbolic forms. In Kant's philosophy, Cassirer considers the "rule of unders tanding" to have a fundamental role in the creation of temporal-spatial relations. Therefore, he does not consider Euclidean geometry to be a necessary correlation of the a priori form of spatial perception in Kant's philosophy. Due to the necessary exis tence of invariant conceptual forms (such as time, place, number and function) in theories, Cassirer also considers comparisons between theories to be possible and that it can be concluded that with the advancement of science they become more comprehensive (in terms of explanatory scope) and more refined (in terms of the abandonment of subs tantive views). As a result, the transition from earlier to later scientific theories is not random and optional and is a function of objective necessity; however, physical theory is not the highes t form of cognition and, along with other symbolic forms, is part of human symbolism.