Why is "Kedoshim tihyu" (Lev. 19) interposed between the chapters about illicit relations?

Question

Chapter 18 of Vayikra (Leviticus) mostly deals with various forbidden relationships, but without specifying the individual punishments for transgressing them (just a collective warning to the nation that tolerating such behaviors will cause them to be "vomited out of the Land," and a brief mention of kareis for the perpetrators).

In ch. 20 the list is repeated (with variations in the ordering of the various relatives), and with penalties specified for each one - some court-imposed punishments, others Divine ones.

In between, in ch. 19, is a miscellany of mitzvos (Rashi to 19:2, citing Sifra, characterizes it as a section on which "most of the fundamental teachings of the Torah are dependent"), starting with "Kedoshim tihyu" - "You shall be holy" (which Rashi explains as meaning: "Separate yourselves from sexual immorality and from sin," and Ramban as saying: "Sanctify yourself within the permissible" - i.e., don't indulge your appetites just because the food or whatever is kosher).

Why this order? I'd think that chs. 18 and 20 should be juxtaposed, with ch. 19 either preceding or following them.

Answer 1

People are not normally inclined to violate the litany of arayos listed. Yet, the generation of the midbar cried when these arayos were prohibited to them (Yoma 75a). This is because the people had no inclination so do evil, and they were upset that they therefore did not have the opportunity to overcome temptation. They therefore incited passions within themselves: "התאוו שיהיה להם תאוה" (Rabbeinu Bechaye, Bamidbar 11:4). As a result they ended up with strange and uncontrollable appetites, such as for eating quail that they knew was deadly. Since they did not want to be forced to lack an evil inclination, they were punished with a forceful and uncontrollable evil inclination (Introduction to Shev Sh'maitsa).

Perhaps a lesson we can learn from the placement of kedoshim tihyu is to restrain ourselves from excessively indulging our passions, lest our passions overcome us and lest we inexorably descend into the mire of new, strange, and destructive appetites.

Answer 2

I would assume that only people who have become holy, developed self-control, love their neighbor like themselves, and the like, can claim sufficient moral outrage to carry out the death penalty if on rare occasion the national conscience is shocked by a strongly taboo sexual act.

Furthermore, the discussion of holiness isn't "go live on a mountain and ignore normal human actions." It's "elevate yourself by taking normal human actions, but showing some restraint." Yes work for 6 days a week like everyone else, but not the seventh. Eat meat for two days but not a third. And so on.

If we don't respect our parents, if we bear grudges, if we don't know how to engage with civilization while sanctifying it, then we have no business claiming we're so holy that we have the right to execute people for their offenses against G-d.