What is the role of Reason in Sikhi?

Reason and Faith are complementary. They operate in different spheres, though each is sovereign in its own field. Reason has certain limits. Faith is necessary in certain basic things, as for example, the existence of God, or the need of the Guru’s assistance. Reason operates in specified fields, as for example, when a man shall pray and what actions he may take. Religion does not exclude the operation of the intellect, though it certainly acts as a limiting factor.

ਅਕਲਿ ਏਹ ਨ ਆਖੀਐ ਅਕਲਿ ਗਵਾਈਐ ਬਾਦਿ ॥ ਅਕਲੀ ਸਾਹਿਬੁ ਸੇਵੀਐ ਅਕਲੀ ਪਾਈਐ ਮਾਨੁ ॥ ਅਕਲੀ ਪੜ੍ਹ੍ਹਿ ਕੈ ਬੁਝੀਐ ਅਕਲੀ ਕੀਚੈ ਦਾਨੁ ॥ ਨਾਨਕੁ ਆਖੈ ਰਾਹੁ ਏਹੁ ਹੋਰਿ ਗਲਾਂ ਸੈਤਾਨੁ ॥੧॥
“Wisdom which leads to arguments is not called wisdom. Intellectual wisdom leads us to serve our Lord and Master; through intellectual wisdom, honor is obtained. Intellectual wisdom does not come by reading textbooks; intellectual wisdom inspires us to give in charity. Says Nanak, this is the Path; other things lead to Satan. ||1||”
(Ang 1245)

Guru Nanak challenged the superstitious practices and rituals of his age. He questioned the value of offering food and water to one’s dead ancestors or the idea that child-birth causes impurity, or that eatable things should be cooked within an encircled space, made sacred by plastering it with cow-dung. He employed the touchstone of reason to test their truth and proved them false. He appealed to men to accept reason as their guide in all such matters.

However, spiritual realization is beyond the ken of reason. On the other hand, great scientists of the world have accepted the higher truths revealed by religion. Man is an imperfect creature and his faculties and powers are limited. Albert Einstein observes: “Strange is our situation here upon earth. Each of us comes for a short visit, not knowing why, yet sometimes seeming to divine a purpose”. Man is unable to comprehend the ultimate reality unaided. He needs the assistance of a religious leader or Guru whose divine knowledge and wisdom can guide him to his spiritual goal.
Science continues to make new discoveries and inventions which, sometimes reject the theories of previous scientist. Could man 30 years ago consider it feasible to orbit through space or land on the moon? What may be regarded as a miracle at one time may become a fact later.
The theory of karam is based on reason, the logic of cause and effect. This means that in order to ensure a good and bright future, man should perform good actions. How can man expect good out of evil actions?
Perhaps it would be best to have a recourse to reason when insensibility or blind faith proves of no avail. But where reason is obliviously not applicable, we must rely on faith. This is particularly true of spiritual matters.