Do you know any name without a reality?
…or have you ever plucked a rose from R, O, S, E?
You have pronounced the name; now go seek the reality it points to.
…know that the moon is in the sky; not in the water of the stream!
If you aspire to rise above mere names and letters;
…purge yourself entirely of your self-images.
Polish away all your attributes; so that you may see your pure untarnished essence.
Behold then; in your own heart; all the knowledge of the prophets
…without book, without tutor, and without guru. ~Rumi 
For Rumi, knowledge encompasses a wide ranging spectrum from the lowest level of awareness to the highest orders. It ranges from mundane know-hows, to practical sciences all the way to sciences of the psyche/soul, through to mystical visions and gnosis at the highest order. Commensurate with knowledge he considers various levels of intellect. Rumi’s works; particularly the Mathnawi; include numerous examples and stories expounding these. He distinguishes between partial or ordinary intellect (aghl-e jozvi); which he also calls discursive intellect (aghl-e bahsi); and Universal Intellect (aghl-e kolli). Universal Intellect or Consciousness is the hidden reality of all existence. Hence; as we shall see later; true knowledge is the knowledge with the power to rend the veils that separate one from one’s true nature; power to reclaim one from one’s self-images veiling the truth.
Ignorance is hundred times better than the kind of knowledge which does not reclaim you from you! ~Sanai 
What can we gain by sailing to the moon if we are not able to cross the abyss that separates us from ourselves? ~Thomas Merton
Two Kinds of Intelligence
There are two kinds of intelligence: one acquired,
as a child in school memorizes facts and concepts
from books and from what the teacher says,
collecting information from the traditional sciences
as well as from the new sciences.
With such intelligence you rise in the world.
You get ranked ahead or behind others
in regard to your competence in retaining
information. You stroll with this intelligence
in and out of fields of knowledge, getting always more
marks on your preserving tablets.
There is another kind of tablet, one
already completed and preserved inside you.
A spring overflowing its springbox. A freshness
in the center of the chest. This other intelligence
does not turn yellow or stagnate. It’s fluid,
and it doesn’t move from outside to inside
through conduits of plumbing-learning.
This second knowing is a fountainhead
from within you, moving out. ~Rumi 
True knowledge is direct, immediate knowledge; knowledge by presence
We use knowing (sense perception, discernment, reasoning, memory, concepts, …) to know things. To respond to a question about the nature of knowing then means we should use knowing to know knowing itself! Is this possible or will it lead into circular and never ending games of definitions behind definitions in one’s head? Rumi; and all the true wisdom masters; teach that yes this is possible.
It is possible only when we remain continually curious, keep seeking the truth and do not stop at conceptual or even spiritual knowledge. While we should respect and utilise our acquired knowledge, we must not take it for granted regardless of its source. Because any knowledge communicated through words or other means is bound to be indirect, it will be pointing to a reality, it will not be the reality itself fully experienced by you. True knowledge is direct, immediate knowledge, also called knowledge by presence which means you become the knowledge.
If your knowledge of fire has been ascertained through words alone;
You must not stop there, seek maturity, be cooked by fire.
There is no direct certainty until you burn; if you desire such certainty, sit down in the fire! ~Rumi 
This might sound too radical, however, such direct knowledge can be experienced through knowing oneself; this is because we are essentially made of knowingness, we are consciousness.
You are consciousness; the rest of you is made of veils covering the consciousness;
Do not lose your true self; do not keep trying in vain. ~Rumi 
The knower is the field, and the known is a form the field assumes without ceasing to be the field.” ~A.H. Almaas 
Take heed lest you lose the sight of wisdom,
lest you lose your self; for the sake of good or bad.
You are the seeker, you are the path, you are the destination too;
beware not to lose your path to your self. ~Suhrawardi 
Becoming one with the object of knowing is possible because that is the actual reality covered by our limited discursive mind trying to figure out reasons and explain reality indirectly.
This Sunlight radiates uncovered; the sheer intensity of the Light veils it.
Before such Sun; which is totally evident; any reasoning would be redundant and misleading. ~Rumi 
Reality is contiguous, there are no disconnections.
Ordinarily we feel ourselves separate from the rest of reality. We strive for connection because that is our true nature. That is why we constantly seek relationships; most of which fail or are full of ups and downs, hurt and temporary happiness. We move on to other relationships, because we mistake relationship with relatedness. Underneath the appearances, everything that exists is already connected and inherently related to everything else:
Nothing that exists is ever unconnected from the Source;
There’s no doubt whatsoever in such continual connection.
Because there are no discontinuities in the spirit, no connection-disconnection;
while the mind cannot think except in terms of connection-disconnection. ~Rumi 
How to attain true knowledge
True knowledge is not something to attain; because attained or acquired knowledge would still be conceptual; it would be something owned by one, added to one. It will not be direct and immediate knowledge. As stated above, one becomes true knowledge by uncovering one’s true self. Hence, the most relevant question would be: how do I know my true self, my essential self? Aspects of this question were dealt with in a previous article: “Dear Rumi…Why am I here? Tell me about work and life purpose.” Let us now expand on it.
Acceptance of who you are, just the way you are
You will not be able to know and be your essential self by denying or rejecting who you take yourself to be at the moment. You need to begin by accepting all of your aspects and attributes as you are. Purging your attributes and self-images begins by acceptance and advances through understanding. We use our ordinary intellect to recognise all our self-images.
The Guest House
This being human is a guest house.
Every morning a new arrival.
A joy, a depression, a meanness,
some momentary awareness comes
as an unexpected visitor.
Welcome and entertain them all!
Even if they are a crowd of sorrows,
who violently sweep your house
empty of its furniture,
still, treat each guest honorably.
He may be clearing you out
for some new delight.
The dark thought, the shame, the malice.
meet them at the door laughing and invite them in.
Be grateful for whatever comes.
because each has been sent
as a guide from beyond. ~Rumi 
Love of the truth shall shatter all that is not you
Once we learn to stop rejecting our experiences; once we stop trying to change ourselves according to our acquired knowledge and cultural values; we would then be more receptive to the truth and capable of utilising our partial intellect and our other capacities to delve deeper; with love of the truth.
The Truth bestows the light upon the souls; the receptive ones shall harvest plentifully in their gowns.
Whosoever lacks a gown of love; shall be deprived of that bestowal of light. ~Rumi 
Among thousands of us in me; I wonder, who am I?
Listen to my roar; do not quiet me down.
I am beside myself; do not lay glass on my path;
If you do, I’ll just walk over them; I’ll shatter whatever I find. ~Rumi
Not-knowing is not ignorance, acquired knowledge is. Not-knowing means not trusting one’s knowledge, wondering about all inner and outer phenomena, and being continually curious and inquisitive. It means uncompromising and continual self-inquiry as a way of life, guided by the Socratic maxim: “The unexamined life is not worth living“.
“When Socrates claims that he knows only one thing; namely that he does not know anything; he is repudiating the traditional concept of knowledge.
Socratic irony consists in pretending that one wants to learn something from one’s interlocutor, in order to bring him to the point of discovering that he knows nothing of the area in which he claims to be wise.” ~Pierre Hadot 
Rumi values inquiry. He also encourages and adopts a not-knowing teaching approach not dissimilar to Socrates. Although Rumi’s style is more of a storytelling type where the questions and answers are told through various characters; making the reader wonder. His method helps bypass one’s mental defences which could be activated through rational discourse (unless the questioner is Socrates! ).
I know that you have clarity, you are not a beginner; your line of questioning is for the sake of the layman. ~Rumi 
Sufi psychology recognizes a state of consciousness which can be best described as bewilderment (hayrat). This is not a state of confusion, on the contrary it is a state of sobriety arising out of detachment from one’s self-images. Rumi refers to a person in such state as Awakened sleeper (khofteh-ey bidar). A quiet contemplative person who might come across as sleep in comparison to people in the busy world; he is however awake and seeing more deeply with his inner eye.
That shall be allotted to the selfless; how can it be shown to those who are ego driven.
Before us, one needs to be an awakened sleeper; in that state of wakefulness he shall dream dreams.
People’s thoughts are the enemy of such sleep; their spiritual throat shall remain blocked while their thoughts are awake.
Bewilderment is needed to sweep the thoughts away; bewilderment devours all thought and recollection. ~Rumi 
Contemplative and reflective practices such as meditation can be extremely helpful. For more on how to use this not-knowing and inquiry process see “Get to know yourself: The ‘Wonder Why Why’ method“.
Rumi urges us to choose simple living, thrift and voluntary poverty (faqr) as a way of being in the world which would facilitate knowing our true self. This is of even higher significance in today’s world where human beings are reduced to consumers! This means that a rigidly conditioned self-image for most is to do with consumerism. ‘Retail therapy’ has become pervasive, it gives the sufferer some temporary relief. Challenging oneself to live a simple life of moderation will surely bring up deep issues of self-worth which one should understand and digest in order to advance closer to one’s essential self.
Try simplicity and thrift for a day or two and you shall find double riches.
Be patient, bear with simplicity, let go of your frustrations;
because in thrift shines the light of the Lord of glory. ~Rumi 
As you simplify your life,
the laws of the universe will be simpler;
Solitude will not be solitude, poverty will not be poverty,
nor weakness weakness. ~Henry David Thoreau
Body movements and spiritual dance
The spiritual dance of Sama (listening or literally, “audition”) which would be conducted with spiritual music; played a major role in Rumi’s transformation in stages of his development after his encounter with Shams (see below). Sama is the dance known today as the dance of The Whirling Dervishes.
The issue of how the body could represent internal states while acting in the exterior world is implicated in stories about great masters’ sama in which they reacted to music through dance. When performed with religious sanction, Sufi dance marked moving bodies as conduits between the interior world and the exterior cosmos filled with movement. 
Rumi’s life exemplifies transmutation of ordinary knowledge into true knowledge
Well, following our own logic, anything that you read here would just be knowledge communicated to you through words; be it Rumi’s words. mine or somebody else’s. Which means it could be helpful but it won’t be true knowledge, unless you begin to practice the methods mentioned and have your own direct personal experience.
Besides so much has been written on this topic that it would be unproductive to repeat them here. For example you might refer to these two articles should you wish to know more about Rumi’s teachings about knowledge. “Rumi’s Masnavi; Knowledge and Certainty” by Franklin Lewis; and “Rumi: Faith, Knowledge, Reason, and Love” by Donald Casey.
So perhaps it is best to conclude with Rumi’s own transmutation account which began subsequent to his encounter with Shams Tabrizi, a wandering rebellious Sufi who sparked an intense spiritual love and became Rumi’s teacher and spiritual companion. To know more, you can read “Who is Rumi“.
Rumi himself summarises it this way:
-Hamid Homayouni (July 2014)
I was dead, I came alive
I was tears, I turned into laughter
The wealth of love arrived
and I turned into eternal wealth.
In essence, I can sum it up in these three sentences:
I went up in flames,
I went up in flames,
and … I went up in flames! ~Rumi