Under what principle is water left by a cat discussed?

Prescribed Acts and Prohibitions: Fard, Wajib, Sunnah, Nafl, Haram, Makruh, Azimah and Rukhsah

• An example of decisive evidence for wajib
• An example showing that every azimah is invalid
• An easing of an original prohibition because of widespread hardship
• An example turning tahrimi into conclusive haram