Taharos, Chapter 8, Mishnah 6. Until now the chapter has been occupied with the chaver and the am ha'aretz and questions of trust. Here the mishnah turns to something entirely different and lays down one of the foundational principles of the whole subject of taharos: which items count as "food" for the purposes of tumah.
"Klal amru b'taharos" - a general rule was stated concerning taharos.
The Rule
"Kol hameyuchad l'ochel adam, tamei." Anything that is designated for human consumption is tamei. The word meyuchad carries the sense of being set aside or earmarked for a purpose, much as the same root is used for "special" in modern Hebrew. And when the mishnah says tamei, it does not mean that the item is actually defiled; it means that it is susceptible to tumah, that it can receive tumah if it comes into contact with it.
How far does this reach? "Ad sheyipasel me'ochel hakelev" - until it becomes unfit even as food for a dog. As long as the food has not deteriorated to that extreme point of rancidness, it retains its status as human food and remains susceptible.
The reverse side: "Kol she'eino meyuchad l'ochel adam, tahor" - whatever is not designated for human consumption is tahor, that is, it cannot contract tumah at all. Such an item stays that way "ad sheyechadenu l'adam", until a person designates it for human use.
What emerges is that certain items sit in a border zone. They could plausibly be treated as human food, or they could just as plausibly be written off as unfit for people, and which of the two they are depends entirely on how a person relates to them.
The Case: The Pigeon in the Winepress
"Keitzad?" The mishnah illustrates. "Gozal shenafal l'gas" - a young pigeon fell into a winepress and died there. Now, we eat the flesh of dead animals all the time in the sense that everything we eat has been slaughtered, but a bird that expired on its own in a vat is not what people ordinarily consider dinner. Its status is genuinely open.
"V'chishav alav l'ha'aloso l'nochri" - if he had in mind to lift it out and hand it over to a non-Jew, saying in effect, here is a fine pigeon for you, then tamei: by that thought he has classified it as human food, and it is now susceptible to tumah.
"Lakelev" - if, when he pulled it out, his plan was to toss the bird to his dog, the ruling is tahor. By that intention he has placed it in the category of something no person would eat, and it therefore cannot take on tumah at all.
"Rabbi Yochanan ben Nuri metamei." This Tanna rejects the distinction altogether: to his mind the pigeon is susceptible to tumah no matter which of the two intentions its owner had.
The Thought of a Cheresh, Shoteh and Katan
The mishnah closes with a fascinating footnote. "Chishav alav cheresh, shoteh v'katan" - what if the one who formed this intention was a deaf-mute, a mentally incompetent person, or a minor?
These three form a classic grouping throughout Shas. They are the standard representatives of a broader category of people who are lav b'nei da'as, who are not considered to possess the settled judgment that halachah relies upon, and who are therefore not treated as responsible agents.
The ruling: tahor. Even if such a person thought clearly that he intends to give the pigeon to a friend, the designation does not take hold. Notice how the mishnah's own language points to why. Chishav comes from choshev, to think, and thinking of this legal weight is exactly what these three are not credited with.
"Im he'eluhu, tamei." But if they actually went ahead and lifted the bird out, it is susceptible to tumah. Talk and intention are one thing; a deed is another. Once they have physically performed the act, the classification stands.
The mishnah spells out the principle: "sheyesh lahen ma'aseh v'ein lahen machshavah" - they have the capacity for action, but not for legally effective thought. When we watch them lift the pigeon out, it is perfectly evident that something has been done. What they cannot supply is the inner designation that alone would have transformed the item's status.
That is the rule of the cheresh, shoteh v'katan, and that is the great klal that the Sages stated concerning taharos.