The Gaon of Vilna is often quoted as saying that the Mesilas Yesharim does not contain a single extra word until chapter eleven. It is not hard to understand the Gaon's meaning, for the change in writing style is immediately evident to every reader. The first ten chapters speak of principles; chapter eleven consists of examples. The author could not be more explicit about this shift; he titled the chapter, "The Details of the Trait of Nekius." This is only chapter name in the book that mentions "details."
Why did the author change his style and give us a long list of detailed examples? The answer can be found in chapter ten.
So now you see the difference between the Zahir and the Naki, even though they are similar. The Zahir is careful with his behavior and makes sure not to sin in ways that he is aware of and are considered by everyone to be sinful. However, he is not yet a master over himself to prevent his heart from being drawn after the natural desires, that it should not influence him with leniencies in areas where the wrongness is not well-known...
This then is the goal of Nekius: achieving mastery over our Yetzer HaRa so as not to be seduced in the grey areas of Halacha where "the wrongness is not well-known." Now we understand why the Ramchal has to delineate specific examples in chapter eleven. By definition, Nekius is gaining awareness and building resistance against the forgotten sins. If the Ramchal doesn't identify them, we would never know what he's referring to. Unless, of course, you are the Vilna Gaon.
II
For years I was troubled by the Ramchal's blatant omission of yichud from chapter eleven. Trumped only by the desire for money, arayos (sexual immorality) comes in second in the Ramchal's list of the most challenging sins. Aside from the primary act, he lists multiple secondary ways arayos can be violated: by touch, sight, speech, hearing, even thought. Surprisingly though, the Ramchal makes no mention of yichud, the prohibition against being alone with a woman. Why did he leave out yichud from his otherwise comprehensive list?
By way of introduction to arayos, the Ramchal quotes an intriguing Midrash. It is understood that the Nazir's primary sin is to drink wine, nonetheless, the Torah also prohibits the Nazir from eating grapes and grape leaves. According to the Midrash, these biblical laws of the Nazir serve as a model for the rabbis, directing them to pass similar legislation for arayos. It is not only the primary sin that should be prohibited, but also anything close to it.
The Ramchal feels this is an important Midrash, but it is hard to see what is new here. The job of the rabbis is known; their mandate is to construct "fences" around the law, prohibiting any act that may lead to a biblical violation. What does the Nazir teach us that we didn't already know?
The answer is that the Nazir is actually introducing an entirely new type of rabbinic law, one that is not a fence at all. If the objective was merely to prevent the Nazir from drinking wine, what is the sense of prohibiting grape leaves? Does eating leaves generate a thirst for wine? Most certainly not. So why does the Torah prohibit it? The answer is that grape leaves have something in common with wine - they both come from the grape vine - and that is reason enough to stay away. This is the remarkable stringency the rabbis learned from the Nazir and applied to arayos: prohibit anything similar to the sin, even if it does not lead to the sin.
The Ramchal underscores this truth in a pointed paragraph.
If a person suggests that what the sages said about verbal vulgarity was just intended to frighten and distance people from sin... but if someone speaks that way just to be funny there is no issue and nothing to be concerned about, tell this person that he is quoting the Yetzer HaRa! ... The truth is what the sages said, vulgarity is literally the arayos of the mouth, it is a prohibited form of promiscuity no different from all the other forms of promiscuity... Even though there is no kares or capital punishment, they are inherently prohibited, apart from their ability to cause and lead to the primary sin itself, just like the Nazir in the Midrash we quoted above.
There are "innocent" acts that must be condemned and prohibited, not because of the proverbial slippery slope, but because their association with sin makes them inherently wrong. This, says the Ramchal, is what the Nazir taught the rabbis about arayos.
It is the very novelty of these laws that drives the Ramchal to write about them. Since these behaviors don't necessarily lead to sin, people don't see the problem. The wrongness is not well-known. Nonetheless, they are a form of arayos and to be Naki from arayos requires Nekius from these behaviors too. Yichud, however, belongs to an entirely different category. The sages did not ban Yichud because it is a form of arayos, they banned it because it leads to arayos. Abstaining from being alone with a member of the opposite sex is simply common sense; one who is permissive is not only in violation of a well-known law, he is grossly negligent. Forget Nekius, this person lacks basic Zehirus! This is why yichud does not belong in chapter eleven.
