If a claim lacks sufficient evidence and reason to support it, say the rationalists, then we ought to either reject it or suspend judgment. Using this powerful method, humankind has extended the frontiers of scientific knowledge in the past four centuries. In fact, the bulk of humanity at one time or another has considered rationalists most dangerous, for by questioning the cherished beliefs they have threatened the sacred cows of society. They may have served a function when they originated, but have since lost that. A good case in point of the persistence of traditional ideas and the difficulty in overturning them is astrology.
Rationalism has deep roots in human civilization.
Its first use appeared with the growth of philosophy in classical Greece and Rome, with the Charvaka materialists of ancient India, and the Confucians of China. Concept and percept, reason and experience, each play a role in testing ideas. In the modern world rationalism has made major strides for it was related to pragmatism, i.e., theories have consequences and may be tested by their applied results. This led to the rapid development of technology, especially during the Industrial Revolution of the eighteenth and nineteenth centuries and the Information Revolution of the twentieth century. This has increasingly expanded the powers of humans over nature.