to these substances until they leave the places where they were formed. To describe them as impure while they remain there is therefore to attribute to them a quality they do not possess.

Second, a defining characteristic of impurity is that it must be avoided during prayer. This requirement does not apply to blood and other substances within the body. Do you not see that the prayer of someone carrying a sealed vessel containing blood is invalid? If you say, “It is excused because of the difficulty of avoiding it,” I reply, “Rather, it is deemed pure because of the difficulty of avoiding it.” What precludes this, when the Messenger of Allah, may Allah bless him and grant him peace, explains the purity of cats by the difficulty of avoiding them, saying:

“It is not impure; it is among those, male and female, who move about among you”?

Indeed, I would go further: we have seen that difficulty in avoidance is a consideration that warrants concessions. If avoiding an entire category is difficult, the whole category is exempted and consequently deemed pure. If the difficulty concerns only part of it, only the amount that is difficult to avoid is exempted. Here, it is difficult to avoid everything inside bodies, so this entire class is deemed pure, just as cats and smaller creatures are. This constitutes a third argument.

The fourth argument is that blood regarded as foul, whether within bodies or elsewhere, is one of the essential constituents of a living creature, without which its life cannot be sustained—so much so that it is called nafs (life). Thus, to hold