We all know that there's a value of Pirsumei Nisa in lighting Chanukah candles, but one thing that comes very strongly out of reading the Rambam on this issue is how central that value is.
(ה) אֵין מַדְלִיקִין נֵרוֹת חֲנֻכָּה קֹדֶם שֶׁתִּשְׁקַע הַחַמָּה, אֵלָא עִם שְׁקִיעָתָהּ--לֹא מְאַחֲרִין, וְלֹא מַקְדִּימִין. שָׁכַח אוֹ הֵזִיד וְלֹא הִדְלִיק עִם שְׁקִיעַת הַחַמָּה, מַדְלִיק וְהוֹלֵךְ עַד שֶׁתִּכְלֶה רֶגֶל מִן הַשּׁוּק; וְכַמָּה הוּא זְמָן זֶה, כְּמוֹ חֲצִי שָׁעָה אוֹ יָתֵר. עָבַר זְמָן זֶה, אֵינוּ מַדְלִיק. וְצָרִיךְ לִתֵּן שֶׁמֶן בַּנֵּר, כְּדֵי שֶׁתִּהְיֶה דּוֹלֶקֶת וְהוֹלֶכֶת, עַד שֶׁתִּכְלֶה רֶגֶל מִן הַשּׁוּק; הִדְלִיקָהּ וְכָבְתָה, אֵינוּ זָקוּק לְהַדְלִיקָהּ פַּעַם אַחֶרֶת. נִשְׁאֲרָה דּוֹלֶקֶת אַחַר שֶׁכָּלְתָה רֶגֶל מִן הַשּׁוּק--אִם רָצָה לְכַבּוֹתָהּ אוֹ לְסַלְּקָהּ, עוֹשֶׂה.
(5) One does not light Chanukah candles before sunset, but rather when it sets, not delaying or lighting in advance. If one forgot, or intentionally delayed, and did not light with the setting of the sun, continue and light until people have stopped passing through the marketplace. And this is about half an hour of more. Once this time has passed, one does not light. And one must put enough oil in the lamp for it to remain lit until people have stopped passing through the marketplace. If it was lit but went out, there is no need to light it a second time. If it remains lit after people have stopped passing through the marketplace, if one wants to extinguish it or remove it, s/he may do so.
(ט) ... הִדְלִיקוֹ מִבִּפְנִים, וְהוֹצִיאוֹ דָּלוּק וְהִנִּיחוֹ עַל פֶּתַח בֵּיתוֹ--לֹא עָשָׂה כְּלוּם: עַד שֶׁיַּדְלִיקֶנּוּ בִּמְקוֹמוֹ. אָחַז הַנֵּר בְּיָדוֹ וְעָמַד, לֹא עָשָׂה כְּלוּם, שֶׁהָרוֹאֶה אוֹמֵר, לְצָרְכּוֹ הוּא עוֹמֵד....
...If the candle was lit indoors and brought outside, and set next to the entrance of the house, the mitzvah is not fulfilled; it must be lit in its place. One that holds the candle in in his/her hand and stands [outside] has not fulfilled the mitzvah, because one who sees him/her will say that s/he does so only for his/her own use...
So this value seems pretty clear: if there's no one to see your menorah, the mitzvah isn't fulfilled at all. And yet, we have another statement by the Rambam:
(ח) בִּימֵי הַסַּכָּנָה, מַנִּיחַ נֵר חֲנֻכָּה בְּתוֹךְ בֵּיתוֹ מִבִּפְנִים; וְאַפִלּוּ הִנִּיחוֹ עַל שֻׁלְחָנוֹ, דַּיּוֹ. וְצָרִיךְ לִהְיוֹת בְּתוֹךְ הַבַּיִת נֵר אֶחָר, לְהִשְׁתַּמַּשׁ לְאוֹרוֹ...
During times of danger, a person may place the Chanukah candle indoors, and it is even sufficient to place it on his/her table. And there must be another lamp in the house so that its light can be used...
What's the purpose? If the candles are only valued for their role in publicizing the miracle, then what to you accomplish by lighting inside? I can imagine an exemption for danger, but if the Rambam really believes that the only value is Pirsumei Nisa, then the exemption might as well extend to the entire act, for all the good that lighting indoors accomplishes.
But it turns out that the Rambam's hands were tied: the exemption to light inside is clear in the Gemara:
... ת"ר נר חנוכה - מצוה להניחה על פתח ביתו, מבחוץ, אם היה דר בעלייה מניחה בחלון הסמוכה לרה"ר, ובשעת הסכנה מניחה על שלחנו ודיו...
...Our Sages taught: The Chanukkah candle - it is a mitzvah to place it at the door of one's house, on the outside, and if one is living in an attic, place it in a window facing the public area. And in times of danger, one may place it on his/her table, and that is sufficient...
What might the Rambam see as the purpose of this exercise? We don't have many clues, because other than making sure you have a shamash to avoid using the menorah on your table, the Rambam doesn't give many parameters for lighting in this circumstance. The parameters we have from other halachic authorities, though, provide something of a mixed message.
(ב) ... הַגָּה: יֵשׁ אוֹמְרִים שֶׁבַּזְּמַן הַזֶּה שֶׁמַּדְלִיקִין בִּפְנִים אֵינוֹ צָרִיךְ לִזָּהֵר לְהַדְלִיק קֹדֶם שֶׁתִּכְלֶה רֶגֶל מִן הַשּׁוּק (דִּבְרֵי עַצְמוֹ וְטוּר בְּשֵׁם תּוֹסָפוֹת), וּמִכָּל מָקוֹם טוֹב לִזָּהֵר גַּם בַּזְּמַן הַזֶּה...
(2) ...Re"ma: There are those who say that in this time, when people light indoors, there is no need to be careful to light before people stop passing through the marketplace (these are his own words, and the words of the Tur, quoting Tosafot), and regardless, it is good to be careful even now...
(יא) (יא) כל הלילה - עד עמוד השחר, ובברכה. והיינו דוקא אם בני הבית נעורים. אבל אם ישנים אין לברך עליהם, אלא ידליק בלא ברכה דכמו דלדידהו לא היה מברך אלא בזמן פרסום הנס...
[If one did not light at the appointed time, s/he may go ahead and light] all night - Until daybreak, and with a blessing. And this is specifically when the people of the house are awake. But if they are sleeping, do not make a blessing over them [the candles], but rather light without a blessing, in accordance with the opinion that one should not make a blessing unless it is at a time of publicizing the miracle...
So, on the one hand, it's preferable to leave the candles lit for the full thirty minutes, to do the mitzvah to the fullest extent possible. On the other hand, if there's no one there to see it, you shouldn't make a bracha, because this lighting may not count as a mitzvah at all.
On a simple level you could just see this as halachic base-covering But I think there's a greater message here, one that's more deeply connected to the story of Chanukah itself. There's a famous question that arises about the story of the oil. Why were the Jews so concerned about lighting with pure oil? The entire nation was impure, and in that circumstance, we have a halachic principle that the rules of purity are suspended. This is mainly established in Pesachim, through discussion of purity and the Korban Pesach:
...אמר רבה,קסבר רבי אליעזר,אין שוחטין וזורקין על טמא שרץ, וכל שאילו ביחיד נדחה בציבור עבדי בטומאה מי,...טומאה דאי כוליה ציבורא טמאין נינהו לא מדינן עלייהו אלא עבדי בטומאה...א"ל רב הונא בריה דרב יהושע לרבא,והרי פסח שני דליתיה בציבור ואיתיה ביחיד...
... Rabah Said: One may not slaughter [the Passover sacrifice] and sprinkle [its blood] for him who is unclean through a reptile, and wherever an individual would be relegated [to the second Passover], in the case of the community they keep [it] in uncleanness... [in the case of] uncleanness, where if the whole community is unclean we do not sprinkle [the water of purification] upon them but they keep [it] in uncleanness... R. Huna son of R. Joshua said to him: Yet there is the second Passover, which is not [practiced] in the case of a community, yet it is [practiced] in the case of an individual...
... סברוה דלכולי עלמא טומאה דחויה היא בציבור ובעי' ציץ לרצות דליכא תנא דשמעת ליה דאמר טומאה הותרה בציבור אלא רבי יהודה דתניא ציץ בין שישנו על מצחו ובין שאינו על מצחו מרצה דברי ר"ש ר' יהודה...
...Now it was assumed that all hold that uncleanness is overridden in the case of a community, hence the headplate is required for propitiation. For there is no [other] Tanna whom you know to maintain [that] uncleanness is permitted in the case of a community but R. Judah...
רש"י פסחים ע״ז א
דחויה - אף על גב דאכשרה רחמנא למיתי בטומאה - לאו היתר גמור הוא, אלא היכא דלא מישתכחי טהורין, וכיון דלאו היתר גמור הוא - בעיא ציץ לרצויי.
Rashi on Pesachim 77a
Overridden- Even though G-d makes it allowable for those who are unclean from the dead, this is not full permission; rather, it just is in the case of there being few pure people, and therefore it is not full permission, and so the headplate is called upon to propitiate.
This is a bit in the weeds, but essentially, the debate that comes out of these sugiyot is the degree of exemption that the community gets for the rules of purity when the whole community is impure. Is it a full and total permission, or just a temporary override because of the extreme nature of the situation? Ultimately, applying this to Chanukah, it's fairly clear that the nation, all impure after a war, would have permission to resume lighting the menorah with impure oil until the larger situation could be rectified. But the people weren't satisfied with that concession to adverse circumstances. Even when they were exempt, they went the extra mile to do the mitzvah as best they could, and G-d met them halfway.
And that, I think, is the value embodied in lighting the candles even when Pirsumei Nisa can't be accomplished. In the face of adverse circumstances, you do the mitzvah to the fullest extent you can. Maybe you can't publicize the miracle of Chanukah to the world, but you can do so to your family, or you can reinforce it just for yourself. Do your best, and G-d might meet you halfway.