answer:Out of context, Nietzsche is saying that the truth isn’t always appetizing. It won’t always make us happy or appeal to us. But an enlightened person realizes that not knowing what is true in no way changes the facts, so there’s nothing to gain—and everything to lose—by avoiding the truth. Only if you know what is true can you plan accordingly. But you can’t just know something, you have to understand it. Understanding is deeper than just knowing, and people who just learn facts without understanding how to apply them are being shallow. In context, the quote means much the same thing. But the passage—which is from Thus Spoke Zarathustra—is about lust and chastity, which many find to be “filthy” topics that are not appropriate for discussion. This is why he uses the language of filthiness in the metaphor.