Method and style of using epistemological resources in each sciences has an important role in the validity and territory of that knowledge. Sadr al-Muta'allehin and Allameh Tabatabaee, despite using axiomatic premise and argumentative method to prove philosophical propositions, also use other epistemological sources, but they are not the same in the way of using them. The present study uses a descriptive-analytical method to compare the method of Mulla Sadra and Allameh Tabatabaee in using "non-public epistemological sources" and answers the question that what commonalities and differences do the two philosophers have in the way of using the mentioned sources? The research approach shows that Mulla Sadra and Allameh Tabatabaee share in using non-public sources of knowledge to problem making, clarify the problem, and discover the middle term of the argument, But they are not the same in using these sources as the premises of the argument and argument confirmation. Mulla Sadra uses revelatory and intuitive sources and tools in these two positions, while Allameh Tabatabaee does not use these sources not only in the preliminaries but also in the confirmation of philosophical arguments. In this way, in addition to avoiding interpretation by the verdict of revelation, he offers a mathematical system capable of achieving logical certainty.