Negaim, Chapter 2, Mishnah 1. The first perek established the four shades of white that make a patch of skin a nega. This mishnah opens the second perek with a problem that follows directly from that: whiteness is judged by the eye, and the eye is influenced by the skin surrounding it. What happens when the person's own complexion distorts the picture?
The problem
Baheres azah nir'eh bagermani keheh. A baheres is the brightest of the shades, kasheleg, white as snow. Take that intense white and place it on a Germani. The word Germani is connected to gerem, which also means etzem, a bone; the Germani is a person of extremely fair, bone-white skin, and some understand him to be an albino. Against such skin, even a snow-white baheres looks washed out, dimmer than the krum habaytzah, the membrane of an egg. It looks like a bohak, a spot too faint to be one of the mar'os of tumah, and by appearance the man would be tahor.
Vehakeheh bakushi azah. The reverse is equally true. Take a faint spot, no brighter than a bohak, something below the krum habaytzah, and place it on a Kushi, a man whose skin is deep ebony black. By contrast it blazes, and it looks exactly like one of the four shades that render a person tamei.
So the mishnah is confronting a question of appearance: is the shade of a nega determined by how it strikes the eye on this particular person's skin, or by some fixed standard?
Rebbi Yishmael
The next voice belongs to Rebbi Yishmael, who prefaces his ruling with a striking declaration: Benei Yisrael, ani chaparasam, I am an atonement for the children of Israel. Why insert such a line here? One approach: the topic under discussion is negaim, and he is voicing a plea that no Jew should ever be struck with such an affliction, that whatever is coming should fall upon him instead. The Tiferes Yisrael suggests another angle: it was Rebbi Yishmael's consistent manner to speak in praise of Israel, of their comeliness and their fine qualities, as we hear from him in Nedarim and in other places, so the phrase is simply his habitual idiom.
His point about the halachah is this: harei hein ke'eshkero'a. The eshkero'a is a tree, identified by some as a species of cypress, the box tree, whose wood is a tan color. Lo shechorim velo levanim, ella beinoniyim: Jews are neither dark nor pale but of a middle complexion, what we might call a Mediterranean tan. The question of extremes, in his view, is not the ordinary case at all.
Rebbi Akiva
Rebbi Akiva looks for his model to the trade of the artists who decorate walls and buildings: yeish latzayarim samanim. Such craftsmen work with a whole set of dyes, shehein tzarim tzuros shechoros, levanos ubeinoniyos, so that they can render their figures dark, light, or in the tan tone that sits between the two extremes.
His practical solution: meivi sam beinoni umakifo mibachutz veteira'eh kabeinoni. One brings the intermediate, tan pigment, encircles the nega with it from the outside, and then the nega is viewed as though it were set in the skin of an average person, neither pale nor dark, and its true shade can be assessed. The mishnah does not specify whether this test is applied to both the Germani and the Kushi or only to the Kushi.
Rebbi Yehudah
Rebbi Yehudah lays down a rule of interpretation: mar'os nega'im lehakeil, the shades of negaim operate in the direction of leniency, aval lo lehachmir, and never in the direction of stringency. The Rav traces the reasoning to a pair of expressions that appear alongside each other in Toras Kohanim. One verse speaks of be'or besaro, the skin of his own flesh, which anchors the measurement in this particular man and his particular coloring, a subjective yardstick. A second verse speaks of be'or habasar, human flesh described in general terms without reference to any one individual, an objective yardstick.
Rebbi Yehudah divides the two cases accordingly, and in both directions the ruling comes out lenient. For the Germani we apply be'or besaro: we look at the nega in his own pale skin, where it appears dim, and he is tahor. For the Kushi we refuse to rule stringently merely because the spot flares against his dark skin; instead we run the test, surrounding it with the tan pigment and seeing how it would look in the skin of a man of the middle, eshkero'a complexion, and only then decide whether he is tamei. In this way both phrases are honored, be'or besaro by the Germani and be'or habasar by the Kushi, and each is honored in the direction of leniency.
The Chachamim
VeChachamim omrim: zeh vazeh kabeinoni. Both the Germani and the Kushi are assessed against the intermediate shade. The Rav points out that this anonymous ruling is in fact the position of Rebbi Akiva, who introduced the pigment. The Tosafos Yom Tov explains why it is presented anonymously: Rebbi Yehudah HaNasi, who arranged the Mishnayos, held that the halachah follows Rebbi Akiva, and so he recorded that view as stam, as though it were the view of the Chachamim at large.
The Ra'avad's understanding of the dispute
The Tosafos Yom Tov cites the Ra'avad, one of the Rishonim, who wrote a commentary on Toras Kohanim, the Sifra on Vayikra, where the parshiyos of Tazria and Metzora and all the inyonim of negaim are found.
According to the Ra'avad, Rebbi Yishmael goes entirely lekula: the Germani and the Kushi are simply never rendered temei'im by a nega, lefi she'einanu yecholim la'amod aleihem, because looking at such skin makes it impossible to establish the true shade of the tzara'as. Since the color cannot be determined by sight against their complexion, we are lenient and declare them tahor on the spot.
Rebbi Yehudah, on this reading, takes a middle position and separates the two cases. With the pale Germani, be'or besaro produces the lenient result, since against his own complexion the patch registers as faint. With the Kushi, we decline to rule severely simply because the spot blazes against dark skin, and instead the tan dye, the sam beinoni, is brought in to put the shade to the test.
And Rebbi Akiva disagrees with Rebbi Yehudah's framework altogether. He holds that the matter is not decided by leniency or stringency at all; rather, in every case we bring the samanim, the intermediate tan pigment, and view the nega as though it sat in the skin of an average person. His is an objective standard, and it is the standard the Mishnah presents as the accepted halachah.