From Beyond Good and Evil, aphorism 11:
"How are synthetic judgments a priori possible ?" Kant asked himself - and what really is his answer? "By virtue of a faculty" but unfortunately not in five words
"By virtue of a faculty" - he had said, or at least meant. But is that an answer? An explanation? Or is it not rather merely a repetition of the question? How does opium induce sleep? "By virtue of a faculty," namely the virtus dormitiva, replies the doctor in Moliere, Quia est in eo virtus dormitiva, Cujus est natura sensus assoupire.
[Because there is in it a dormitive virtue,
whose nature it is to send the senses to sleep.]
But such replies belong in comedy, and it is high time to replace the Kantian question, "How are synthetic judgments a priori possible?" by another question, "Why is belief in such judgments necessary?" - in effect, to realise such judgments must be believed to be true, for the sake of the preservation of creatures like ourselves; though they might, of course, be false judgments! Or, speaking more plainly: synthetic judgments a priori should not "be possible" at all; we have no right to them; in our mouths they are nothing but false judgments. Only, of course, the belief in their truth is necessary, as a foreground belief and visual evidence belonging to the perspective view of life.
If you know nothing about Kant or what "a priori" even means than this passage doesn't mean much other than some pedantic quibbling about epistimology. With the philisophical and historical background in Kant, and in N's philosophy as a whole you'd know 1) Kant was extraordinarily influential and 2) a priori judgment is one of the essential epistimological of Kant and is, according to him, a basis for all human knowlege. If one beleives in the "truth" of a priori judgment then, according to Kant, they can live in a certain way and "know" right from wrong, without the need for a divine authority.
Aphorism 13 from Beyond Good and Evil:
Physiologists should think before putting down the instinct of self-preservation as the cardinal instinct of an organic being. A living thing seeks above all to discharge
its strength---life itself is will to power;
self-preservation is only one of the indirect and most frequent results
In short, here as everywhere else, let us beware of superfluous
teleological principles---one of which is the instinct of self-preservation (we owe it to Spinoza's inconsistency). Thus method, which must be essentially economy of principles, demands it.
So if you don't know what "teleological princples" means you can look it up and find that "Teleology or finality is a reason or explanation for something in function of its end, purpose, or goal.". So you might think "ok, so self-preservation isn't a goal, it's just something that happens". But if you knew about the history of teleology, you'd know that it was the basis of the entire understanding of the world. Aristotle's view of the world is founded on the principles of teleology, and Christian thinkers like Aquinas would use teleology to argue for the existence of God.
If you don't know the history of the ideas you might just think he's complaining about the mistakes of previous philosophers. But he's doing more -- he's illustrating how entire worldviews
, the things that people in the past thought were the most important things, the essential truth of the world, are, at best, convenient interpretations.