Philosophers have divided philosophy into general and special categories and believe that special philosophy deals with components of life. The selected viewpoint as to the quality of philosophy is that it deals with different features of human self. This definition allows us to discuss, on a wide scale, all kinds of combined philosophies that attend to realities. One of those combined philosophies is the philosophy combined with sciences with a historical and logical approach, which is also known as gate-keeping theory, which allows the researcher to take a secondary approach to external questions of sciences and discover the relationship between different scientific disciplines. That discovery not only answers questions related to combined philosophy and external scientific questions, but also turns into the most important method for discovery and establishment of interdisciplinary sciences, especially if we considered science as a common axis to which certain rules and features apply. This paper, tries to first provide a definition of choice for the modern Islamic knowledge as well as the quality and types of combined philosophy and a standard theory to claim that a combined philosophical approach to sciences or gate-keeping theory is the most important method to discover interdisciplinary sciences and that we must not stop at interdisciplinary sciences that have been thus far discovered.