Below is a summary of an essay by Muhammad Este'lami on 'The Concept of Knowledge in Rumi's Mathnawi' in 'The Heritage of Sufism Volume 1'
Rumi's definition on ilm (knowledge) in his masterpiece Mathnawi is somewhat paradoxical in that it is both similar to and different from the normal convention. Rumi's take on knowledge could give its seeker much more. It is a way of learning and understanding that could lead to peace and spiritual satisfaction. It pertains to an invisible school inside man's heart and the mysteries only visible via inner vision.
Rumi himself was a learned man. He was very well trained in Qur'an, jurisprudence, prophetic traditions, Islamic philosophy and literature. His scholastic knowledge however did not live up to his spiritual expectations. In the 6th Volume of his Mathnawi he wrote:
"Though you believe in the accuracy of the scholastic knowledge, it will not open your inner eyes to invisible existence."
In Mathnawi he defined two categories of ilm. One concerns the visible and material existence and the other is not worldly. The latter will give one comprehension on the Truth or an awareness of an invisible world which is real and eternal. An anecdote below describes this difference better.
A conceited grammarian (nahwi) embarked on a boat and asked the boatman: "Have you ever studied nahw (grammar)? When the boatman said that he had never studied grammar, the nahwi said to him: "O! I feel so sorry for you, half your life has gone for naught." The boatman did not answer immediately and kept silent for a while until the wind cast the boat into a whirlpool. Then the boatman shouted: "Do you know how to swim?" The proud grammarian said that he would never be able to swim. The boatman said: "O Nahwi! Your whole life has gone for naught, because the boat is sinking in this whirlpool."
In response to this story, Rumi said:
"Here what is needed is self-effacement (mahw) not grammar (nahw). If you're effaced from self, then plunge into the sea, and be not frightened of any peril or danger."
For the window to the invisible world to open we need "jurisprudence of jurisprudence" (fiqh-i fiqh), the "morphology of morphology (sarf-i sarf) and the "grammar of grammar" (nahw-i nahw). This knowledge is obtainable "from That Source" (az an sar), a type of knowledge that grows from a Divine root.
The gate of the heart can only be opened by God. And only a master or murshid can guide a disciple. A murshid therefore must be obeyed as a prophet.
"Keep silent, so that you may hear from the speakers,
that which may not come into utterance or into explanation.
Keep silent so that you may hear from the Sun
that which may not come in books or into allocution.
Keep silent so that the Spirit may speak for you.
In the Ark of Noah leave off swimming."
Rumi further described the differences between the two types of knowledge. A man who has inward or esoteric knowledge (ilm-i batin) which is Divine ilm and thus comprehend the mysteries of the invisible existence is a muhaqqiq (realizer). A man who studies the same subject through scholastic programs is a muqallid (imitator) because he merely imitates words without having awareness of their realities or inward meanings.
"Between the realizer and the imitator, there are many differences. The former is like David and the imitator is only an echo (not a song, not a singer)."
Tahqiq is another term which describes knowledge of the real (Eternal Existence) gained through spiritual realization. Taqlid or imitative knowledge refers to what is taught in the schools.
"Conventional knowledge is only for sale or self-advertisement. When it finds a purchaser, it glows with delight. The purchaser of real knowledge is God. And for such a knowledge, the market is always flourishing."