Purity is the state in which one must be in to safely come in contact with the divine. It's primarily associated with being able to offer sacrifices in the Temple.

​

וְגַ֧ם הַכֹּהֲנִ֛ים הַנִּגָּשִׁ֥ים אֶל־יְהוָ֖ה יִתְקַדָּ֑שׁוּ פֶּן־יִפְרֹ֥ץ בָּהֶ֖ם יְהוָֽה׃

The priests also, who come near the LORD, must stay pure, lest the LORD break out against them.” (Exodus 19:22)

אוֹ־אִישׁ֙ אֲשֶׁ֣ר יִגַּ֔ע בְּכָל־שֶׁ֖רֶץ אֲשֶׁ֣ר יִטְמָא־ל֑וֹ א֤וֹ בְאָדָם֙ אֲשֶׁ֣ר יִטְמָא־ל֔וֹ לְכֹ֖ל טֻמְאָתֽוֹ׃

or if a man touches any swarming thing by which he is made unclean or any human being by whom he is made unclean—whatever his uncleanness—

נֶ֚פֶשׁ אֲשֶׁ֣ר תִּגַּע־בּ֔וֹ וְטָמְאָ֖ה עַד־הָעָ֑רֶב וְלֹ֤א יֹאכַל֙ מִן־הַקֳּדָשִׁ֔ים כִּ֛י אִם־רָחַ֥ץ בְּשָׂר֖וֹ בַּמָּֽיִם׃

the person who touches such shall be unclean until evening and shall not eat of the sacred donations unless he has washed his body in water.

וּבָ֥א הַשֶּׁ֖מֶשׁ וְטָהֵ֑ר וְאַחַר֙ יֹאכַ֣ל מִן־הַקֳּדָשִׁ֔ים כִּ֥י לַחְמ֖וֹ הֽוּא׃

As soon as the sun sets, he shall be clean; and afterward he may eat of the sacred donations, for they are his food. (Leviticus 22:5-7)

 

(The Hebrew word/root translated as pure is the same as the word translated as clean.) 

​

There are a ton of examples of things, primarily in Leviticus, that can make one tameh, ritually impure. Rashes, illness, childbirth, ejaculation, death, touching dead things, touching sick people, etc. (Houses can also become impure if they have certain types of mold.)

​

It's important to understand that purity is a temporary state. There's nothing morally wrong with being impure—in fact, even when there was a Temple, most Jews were in states of ritual impurity most of the time. That doesn't mean they were bad people. It means they were living their lives. Kohanim (priests) and Levites were required to be ritually pure more often, but that's because it was their job to manage the whole sacrificial system. 

​

To use a modern analogy, a surgeon has to remain in a state of extreme cleanliness far more of the time than the rest of us, because her job requires it. That doesn't mean that the rest of us are somehow worse people than the surgeon—living your life brings you in contact with bacteria, and most of the time, that's fine. It's just that if you're going to cut people open and stick your hands inside them, staying as bacteria-free as possible while doing that is pretty crucial.

​

If I had to try to simplify the concept of what taharah and tumah actually are, I'd say that tumah, ritual impurity, has to do with transitional states. There's a sense, in the Torah, that birth (and by extension, pregnancy and ejaculation) and death (and by extension, sickness and menstruation) partake in some way of otherworldliness, of instability. There's nothing wrong or evil about that—after all, it's a commandment to reproduce, and the birth of a baby is a good thing; it's also a commandment to tend to the dead—but they are areas that have to be treated with caution.

​

And something about them, perhaps that very instability, makes them unsafe states in which to come in contact with holiness, with that divine radiation. You don't cross those streams.

 

A state of purity is unsustainable, and that's by design. It's essentially a frozen moment, a state in which ordinary life stops and nothing changes so that one can focus on facing the absolute.

​

A function of using ritual impurity to bar people from Temple worship is, in part, to set apart people who've just gone through major life transitions (having a baby, losing a loved one) from (at the time) the normal rhythm of participation in ritual activities. If you're sick, or if you've just had a baby, or if you've just lost a loved one, you should take time away from public life and focus inward, on yourself and your family.

That doesn't mean there's something unholy about impurity. Strangely, as I mentioned above, touching a Torah scroll—the most sacred object in Judaism—makes your hands impure (see a fascinating debate about what that means here). Indeed, the primary sources of impurity, birth/reproduction and death, are in some ways associated with the divine. God breathes life into humans, after all, and the way to give the part of one's flock that is owed to God is to sacrifice it—that is, to kill it. (It's also irrelevant to "holiness" when it's used in reference to people—Israel is supposed to be a holy nation, but its members can't be ritually pure all the time.)

​

There's a somewhat radical passage from the Mishnah (compendium of early debates about Jewish law) that talks about what is and isn't impure.

​

אוֹמְרִים צְדוֹקִים, קוֹבְלִין אָנוּ עֲלֵיכֶם, פְּרוּשִׁים, שֶׁאַתֶּם אוֹמְרִים, כִּתְבֵי הַקֹּדֶשׁ מְטַמְּאִין אֶת הַיָּדַיִם, וְסִפְרֵי הוֹמֵרִיס אֵינוֹ מְטַמֵּא אֶת הַיָּדַיִם. אָמַר רַבָּן יוֹחָנָן בֶּן זַכַּאי, וְכִי אֵין לָנוּ עַל הַפְּרוּשִׁים אֶלָּא זוֹ בִלְבָד. הֲרֵי הֵם אוֹמְרִים, עַצְמוֹת חֲמוֹר טְהוֹרִים וְעַצְמוֹת יוֹחָנָן כֹּהֵן גָּדוֹל טְמֵאִים. אָמְרוּ לוֹ, לְפִי חִבָּתָן הִיא טֻמְאָתָן, שֶׁלֹּא יַעֲשֶׂה אָדָם עַצְמוֹת אָבִיו וְאִמּוֹ תַּרְוָדוֹת. אָמַר לָהֶם, אַף כִּתְבֵי הַקֹּדֶשׁ לְפִי חִבָּתָן הִיא טֻמְאָתָן, וְסִפְרֵי הוֹמֵרִיס, שֶׁאֵינָן חֲבִיבִין, אֵינָן מְטַמְּאִין אֶת הַיָּדָיִם:

​

The Sadducees say: we complain against you, Pharisees, because you say that the Holy Scriptures defile the hands, but the books of Homer do not defile the hands. Rabban Yohanan ben Zakkai said: Have we nothing against the Pharisees but this? Behold they say that the bones of a donkey are clean, yet the bones of Yohanan the high priest are unclean. They said to him: according to the affection for them, so is their impurity, so that nobody should make spoons out of the bones of his father or mother. He said to them: so also are the Holy Scriptures according to the affection for them, so is their uncleanness. The books of Homer which are not precious do not defile the hands. (Mishnah Yadayim 4:6) 

​

The Sadducees are arguing with the Pharisees because they think it's outrageous that touching a Torah scroll makes one's hands unclean, but touching Homer's work doesn't. Rabbi Yochanan eventually agrees with the Pharisees, who tell him, astonishingly, that the more beloved and precious (and, possibly, holy) something is, the more ritually impure it is.

​

So ritual impurity isn't necessarily the opposite of holiness—they may actually be related. But it's something that's not safe to combine with interaction with the divine, perhaps because it's potentially distracting. 

​

And to go back to the discussion of modern Jewish uses of the mikvah (the primary method for becoming ritually pure), what has survived in practice is a marker of transitional states, which aligns with the idea that ritual impurity is associated with transitions.

​

To complicate matters, anthropologists have been trying to define Jewish conceptions of purity and impurity for a long time, and I'm not sure we're any closer.

​

• Baruch Levine argued in In the Presence of the Land: Aspects of Ritual in Ancient Israel (1974) that the ancient view of impurity was as a state that opened one up to malign influences.

• Robertson Smith (1956) and Yehezekel Kaufmann (1938) argued that ritual impurity was a state that rendered one unfit to deal with the divine.

• Mary Douglas first argued (1966) that rules around purity, especially the rules around kashrut (which foods are kosher) were about maintaining clear categories and boundaries, then changed her mind in 2002 and argued that impure or unclean animals are actually those which are not to be harmed. She believed impurity was both contextual (what might be pure in one context could be impure in others) and associated more closely with the idea of "dirt" than the idea of moral failure.

• Jacob Neusner (1932-2016) did a careful classification of concepts of purity and impurity and their changes over time without really providing new explanations for those classifications.

• Samson Raphael Hirsch (1808-1888) argued that purity was a "clear" state in which one was capable of receiving divine transmission, while impurity was a "blocked" state

• Maimonides (1135-1204) argued that the rules were simply arbitrary and beyond human understanding.