Yaqin (certainty) means having no doubt about the truth of a matter and arriving at accurate doubtfree knowledge through exact verification. Used also to mean verification seeking certainty examining and exerting strenuous effort to arrive at certainty certainty is a spiritual station that a traveler on the path has reached and experienced.
It is obtained only by those who have an innate capability to progress and develop inwardly. This term is not used for God's Knowledge which is infinite and therefore neither increases nor decreases. God does not have a Name by which he is known as "One having certainty or giving certainty." In addition certainty is a degree reached through study and verification of something previously doubted. The Divine Being neither doubts nor needs verification.

According to truth-seeking scholars yaqin means certainty or conviction of the truth expressed in the essentials of faith including primarily one's doubt-free belief in God's Existence and Unity. It is also defined as reaching that conviction through observing or experiencing the originals or truths of those essentials in which regular people believe and discerning or penetrating the realms beyond this material one.

Certainty may also be regarded as a point final in one respect and initial in another reached by using all sources of knowledge and ways of observation and discernment. A traveler who has reached this point frequently sails for what is eternal realizing ascension in his or her heart and reaching the horizon of: His sight swerved not nor did it go wrong (53:17). He or she travels amidst Divine manifestations in the material and immaterial realms and is favored with a tongue to speak eyes to see and ears to hear (the truths contained in) the Supreme Sign. [1] That is repeated observation and study of the book of the universe of the things and events contained in it allows the traveler to eternity to perceive the meanings of the inimitable seals on things and events special to God. [2]

By repeatedly observing and reflecting on the scenes presented for study in the outer world as well as in his or her inner world truths beyond the visible realm are unveiled to the traveler. Also by living in the brilliant mysterious climate of Divine Revelation namely the Qur'an and the Sunna one feels the manifestation of the Hidden Treasure in his or her heart. The believer becomes aware of and experiences the tokens and signs issuing from the prism of his or her conscience which reflects the rays of Divine gifts coming from the outer world his or her inner world and the Divine Revelation and sends them to his or her senses and faculties. Certainty in this meaning and degree is a gift with which God favors those near to Him.

Even in its least degree certainty is so strong that it fills the heart with light removes the mist of doubt from the mind and causes breezes of joy satisfaction and exhilaration to blow in one's inner world. As pointed out by Dhu al-Nun al-Misri certainty causes the heart to overflow with the desire to reach eternity. This engenders the desire to live an austere life for asceticism allows one to think and speak with wisdom. One who takes the wing of asceticism and flies to the realm of wisdom never forgets what the end will be always thinks of the afterlife and always feels God's company even when with other people. [3]

In the early steps of certainty the veil between the material and immaterial sides of existence begins to be removed and a few steps further the traveler discerns the realm beyond this material world. With his or her heart filled with Divine manifestations which result in the attainment of peace and satisfaction the believer is freed absolutely from all doubt about the truths of faith. Like 'Ali ibn Abi Talib may God be pleased with him some who have attained this degree of certainty have declared: Even if the veil between the seen and the Unseen were to lift my certainty would not increase. [4] A few steps further on is the station where one journeys in the pure realm of Divine gifts of which eyes have never seen ears have never heard or minds have never conceived.

To gain certainty an initiate beginning the journey must try to do what is necessary to reach it. However one can only reach this station when God bestows it as a blessing and gift. Without acquiring due knowledge of God one cannot reach certainty. Knowledge of God is acquired through a correct view of and perspective on things and events; the ability to think in a correct and balanced manner; purity of intention; study of the signs of God's Existence and Unity; and reflection on His acts and the manifestations of His Names and Attributes. Knowledge of God is a light illuminating the initiate's inner and outer worlds a light shining from all corners of existence. Under the rays of this light the initiate sees everything as it really is and being freed from the confines of multiplicity (of things and events) discerns Divine Unity and is enraptured with indescribable spiritual pleasure.

Although an initiate may feel uneasy during the early steps of the way to certainty he or she will be lost in inconceivable pleasure and peace at the end of it. Those who cannot distinguish between what is felt in the beginning and what is experienced at the end wrongly conclude that certainty is risky; however those who constantly feel God's company and the resulting spiritual delight enjoy peace and security from all spiritual trouble and possible deviation. Uneasiness and trouble are felt only in the beginning. As for certainty being risky all stations confront the traveler with some degree of risk. The Prophet upon him be peace and blessings declared: Even I would not be able to be saved (from Hellfire or God's punishment through my own actions) if God did not embrace me in His mercy. [5] As for being secure from trouble and deviation and gaining peace these are fresh fruits that God causes certainty to yield.

As referred to in some verses of the Qur'an. Sufis classify certainty in the three categories:

- Certainty coming from knowledge: Having a strong firm belief in or conviction of all the essentials of faith primarily God's Existence and Unity acquired through correct observation and study of the relevant signs and evidence.

- Certainty coming from direct observation or seeing: Having an indescribable degree of certainty and knowledge of God acquired through unveiling and observing the immaterial truths invisible to ordinary believers and on which the essentials of belief are based.

- Certainty coming from direct experience: Being favored with God's constant company without any veils and in a way that only the one receiving this favor can perceive. Some have interpreted it as self-annihilation in God and gaining subsistence by Him.

These three degrees of certainty can be summed up in the following example: A person's knowledge of death (before he or she dies) that is acquired by observing or studying the body in a biological context can be an example of certainty coming from knowledge. Witnessing some metaphysical phenomena such as seeing the angel who has come to remove one's soul and catching glimpses of the intermediate world of the grave may be regarded as a kind of certainty coming from direct observation. The certainty gained by actually experiencing death is a certainty coming from direct experience.

Certainty about abstract truths such as the nature of God's Names and Attributes coming from direct observation for example pertains to one's personal experience. It is therefore beyond my ability to explain.

[1] "The Supreme Sign" is a Qur'anic expression that is generally held to be the sign by which God is known most clearly.
[2] God's signs the signs of His existence and Unity are displayed by everything in the language of wisdom coherence beneficence and relation to other things. It is like a seal designed by Him to prove His Unity.
[3] Al-Qushayri. Al-Risala. 180.
[4] Al-Qari. Asrar al-Marfu'a. 286.
[5] Al-Bukhari. "Riqaq." 18; Muslim. "Munafiqun." 71-8.