Is the criterion for excusing impurity based on it not being discernible by sight?
Chapter on what purification is achieved with regarding water
Al-Mughni
Book of Purification
Primary text
Establishing the criterion for excusing impurity based solely on it not being discernible by sight is invalid. This criterion requires a specific decree (tawqif) from the Lawgiver or its establishment through legal consideration (i'tibar) in a specific context, neither of which is present.
Supporting text
The argument citing hardship as a justification for excusing such impurity is invalid, because rulings are established based on certain knowledge of the impurity's arrival, and in certainty, there is no differentiation in hardship. Moreover, hardship is a rationale (hikmah) upon which a legal ruling cannot be based solely by itself.