Why do rationalists believe that some truths are necessary and universal?

Rationalists believe that certain truths are necessary and universal because they hold that the world is a rationally ordered whole, structured by logical necessity and intelligible to the human intellect. Unlike empiricists, who argue that knowledge is derived from sense experience, rationalists maintain that the mind possesses an innate capacity to directly apprehend a priori truths that transcend sensory perception.123

These truths are considered necessary because they cannot be conceived as otherwise; to deny them would be to fall into a logical contradiction. They are viewed as universal because they admit no exceptions. Rationalists argue that through intellectual intuition, the mind can grasp universals—such as mathematical principles or logical relations—that are not mere habits formed by experience but are instead fundamental to the structure of reality.241

By relying on reason as the ultimate court of appeal, rationalists assert that this a priori knowledge provides the most certain foundation for understanding the world, as it is grounded in the inherent logical structure of existence rather than the tentative and often confused data provided by the senses.12