Why do rationalists consider reason a source of knowledge independent of sense experience?

Rationalists consider reason a source of knowledge independent of sense experience because they believe reality possesses an inherently logical structure that the intellect can grasp directly. Unlike empiricism, which relies on potentially confused or tentative sense perceptions, rationalism asserts that certain fundamental truths—particularly in logic, mathematics, and metaphysics—are a priori and can be apprehended through the intellect.123

Rationalists argue that this knowledge is both necessary and universal, meaning it cannot be conceived as otherwise and admits no exceptions. They maintain that the mind can perceive universals and their relations—such as the nature of triangularity or numerical concepts—which transcend the limitations of sensory observation. Furthermore, many rationalists defend the doctrine of innate ideas, suggesting that the human mind possesses inborn powers of insight that allow for the grasp of self-evident principles. By prioritizing reason as the ultimate court of appeal, rationalists seek to establish a foundation of certainty that they believe sense experience alone cannot provide.341