What is the ruling on studying and applying the science of physiognomy (firasah) that Imam Al-Shafi'i studied, and is it related to a Muslim's belief?

Learning firasah (physiognomy) is permissible, as long as it does not involve claiming knowledge of the Unseen. It is the ability to discern states from outward signs. Firasah is divided into three types: Imaniyyah (faith-based), which is a light that Allah casts into the heart; firasah gained through discipline, hunger, and wakefulness (which applies to both believers and disbelievers); and Khalqiyyah (character-based) firasah, which involves inferring character from physical traits. Firasah depends on the acuity of the observer's mind and the clarity of the signs on the observed person. Firasah can be acquired or a gift from Allah, and it is not permissible for one who possesses it to mislead people into believing they have knowledge of the Unseen.