Tacit knowing is a kind of relational intuition, which leads us to tacitly understand the "synthetic reality" behind the appearance through the overall grasp of the relationship between details. The concept of "synthetic" here implies the synthetic judgment a priori discovered by Kant. In fact, it is an existentialist extension of Polanyi's endeavor to understand the mysterious power of Kant's a priori intellectual framework which can automatically shape experience and conceptual structure. His understanding of the relationship between the whole and details of the synthetic reality in tacit knowing has evolved from a one-way relationship of tacit integration to a complex function of two-way construction.