Firasah is a sense of visual acumen, perception and insight.The firasah is a light which Allah, subhanahu wa ta`ala, deposits in the heart of His servant. By this light, His servant distinguishes between truth and falsehood and between right and wrong.
The reality of firasah is a sharp thought that enters the heart and dominates its opinion. It overwhelms the heart just as the lion does to its pray, fareesah. Note the similarity between firasah and fareesah in Arabic. However, in their linguistic forms, fareesah is an object whereas firasah is similar in form to wilayah (authority and power), imarah (authority and command) and siyasah (administration and leadership).
The strength of firasah is dependent on the strength of faith. A person with stronger faith has sharper firasah. Amr bin Nujaid used to say that whoever lowers his gaze away from prohibitions, restrains himself from vain desires, constructs his interior according to muraqabah (knowledge that Allah is watching over us), his exterior according to the Sunnah, and accustoms himself to eat only halal, his firasah will never be wrong.
Firasah is linked to three human organs: the eye, ear and heart. His eye examines the look and the signs, his ear examines the speech, the over expressions, oblique inferences and hints, content, logic and tone of voice. And his heart analyzes both what is seen and heard to perceive hidden thoughts of others. His analysis and examination of the interior compared to the exterior is like one who examines currency to see if it is counterfeit after examining the outside. It is also similar to Ahlul-Hadeeth (scholars who specialize in the knowledge of the hadeeth), who will read a hadeeth that has a sound isnad (chain of narrators) but upon examination of the matn (text of the hadeeth), it is found that it is a fabricated hadeeth.
There are two factors in firasah. One is the quality of one’s mind, the sharpness of the heart and the intelligence. The second is the appearance of the signs and indications on others. When both factors are present then one’s firasah may not be wrong.
Madarij As-Salikeen, “The Station of Firasah” – Ibn ul Qayyim al Jawziyyah, Translated by Yahya