Why eat maror?

Summary: It is to remind of the bitterness, or from some medical reason? Can we ascribe it to practical cause against the Rabbinic tradition (which also happens to make good sense)? Rashi, Ibn Ezra, Ibn Caspi. Also, how Ibn Ezra is thus frum.

Post: One eats the matza and korban Pesach with the accompaniment of bitter herbs. The pasuk:

ח  וְאָכְלוּ אֶת-הַבָּשָׂר, בַּלַּיְלָה הַזֶּה:  צְלִי-אֵשׁ וּמַצּוֹת, עַל-מְרֹרִים יֹאכְלֻהוּ.

8 And they shall eat the flesh in that night, roast with fire, and unleavened bread; with bitter herbs they shall eat it.

Chazal note reasons for Pesach, Matza and Marror. Their significance seems explicit or else at least alluded to in the pesukim. In terms of korban pesach:

כז  וַאֲמַרְתֶּם זֶבַח-פֶּסַח הוּא לַיהוָה, אֲשֶׁר פָּסַח עַל-בָּתֵּי בְנֵי-יִשְׂרָאֵל בְּמִצְרַיִם, בְּנָגְפּוֹ אֶת-מִצְרַיִם, וְאֶת-בָּתֵּינוּ הִצִּיל; וַיִּקֹּד הָעָם, וַיִּשְׁתַּחֲווּ.

27 that ye shall say: It is the sacrifice of the LORD'S passover, for that He passed over the houses of the children of Israel in Egypt, when He smote the Egyptians, and delivered our houses.' And the people bowed the head and worshipped.

In terms of Matzah:

לט  וַיֹּאפוּ אֶת-הַבָּצֵק אֲשֶׁר הוֹצִיאוּ מִמִּצְרַיִם, עֻגֹת מַצּוֹת--כִּי לֹא חָמֵץ:  כִּי-גֹרְשׁוּ מִמִּצְרַיִם, וְלֹא יָכְלוּ לְהִתְמַהְמֵהַּ, וְגַם-צֵדָה, לֹא-עָשׂוּ לָהֶם.

39 And they baked unleavened cakes of the dough which they brought forth out of Egypt, for it was not leavened; because they were thrust out of Egypt, and could not tarry, neither had they prepared for themselves any victual.

So what of marror? Rashi writes:

and unleavened cakes; with bitter herbs: Every bitter herb is called מָרוֹר, and He commanded them to eat bitters in commemoration of “And they embittered their lives” (Exod. 1:14). — [from Pes. 39a, 116b]

על מררים: כל עשב מר נקרא מרור. וציום לאכול מרור זכר לוימררו את חייהם (שמות א יד):

such that it also has Biblically granted significance. Is this aspect of maror deduced from reasoning and comparison to the other two, or is it tradition? Ibn Ezra regards it as the latter:

יב, ח]
על מרורים יאכלוהו -
אמר אחד מחכמי ספרד:

ידוע כי הליחה תגבר בארץ מצרים בעבור מימי היאור ובעבור שלא ירד שם גשם, כי האויר הוא לח תמיד. על כן מנהגם היה לאכול בכל שלחנם מיני מרורים רבים מעשבים וחרדל ואפילו לא יהיה למצרי אלא פת לבדה, לעולם המרורים יהיו על שלחנו לטבול בו הפת, כי הם רפואה לאוירם.

ואנחנו נסמוך על דעת קדמוננו ז"ל שפירשו לנו, כי המרורים זכר לוימררו את חייהם.

That is, he cited an unnamed one of Chachmei Sefarad who gives a medical reason for maror, such that the Egyptians would always eat types of bitter herbs. Yet Ibn Ezra rejects this, for we rely upon the position of Kadmoneinu who explained to us the the maror is as a remembrance to וימררו את חייהם. 

(There might be halachic repercussions, in terms of sipur yetzias mitzrayim.)

I agree that Chazal's explanation is not intended as some sort of derash, and that given the context of zecher, it seems quite plausible. And looking back, I don't really think much of the contemporary medical theories, such that they would necessarily compel Egyptian practice. (Straightforward knowledge of Egyptian practice in ancient times might be something different.) Perhaps this peshat plausibility is what guides him towards relying upon Chazal, rather than the realia. Or perhaps he would do this regardless.

Of Ibn Ezra's supercommentators, Ohel Yosef sees this as grounds for a defense of Ibn Ezra's frumkeit. That Ibn Ezra sees it as ancient oral tradition, and that this should shut up his critics.

"And we rely on the position of those before us, zal -- to explain, that our rabbis received from the first forefathers, that Moshe said that Hashem commanded that the maror be eaten in token of how the Egyptians embittered the lives of our fathers, as they darshened in the end of masechet Pesachim {116b}. We rely upon them just as we do in all the commandments.

Yosef the supercommentator said: This should also be evidence regarding Rabbi Avraham Ibn Ezra that he relied upon the words of Chazal and leaned upon their explanations in all the commandments, and he never differed with them in explaining the commandments; rather, he explained the peshat upon every verse when it was narrative, rather than commandment. But upon explaining the commandments, he relied upon our holy fathers. And those who say negative things against him should guard their mouths with a muzzle."

I am not so convinced that Ibn Ezra would never differ with Chazal in explaining a pasuk, despite his arguments with Karaites and despite his rejection of this Sefardi Chacham's position. Even if he often comes to approximately the same conclusion, off the top of my head, his rejection of Peru Urevu as a Biblical command, his understanding of mimacharat haShabbat, and his understanding of the Biblical prohibition on shaving all seem to differ from that of Chazal.

Without making the narrative / legal distinction, Mechokekei Yehuda in Yahel Or also uses this comment as a defense of Ibn Ezra against his accusers.

As mentioned in a previous post, Ibn Caspi visited Egypt, in hopes of learning Torah from the descendants of the Rambam. While there, he picked up on some of the Egyptian practices in his day, and turns to realia in order to explain various pesukim in sefer Shemot.

He does not explicitly invoke this here, but I wonder if it plays a role. He does not invoke personal experience. Regardless, Ibn Caspi chooses a medical reason as the reason for maror, despite Ibn Ezra's rejection. And therefore it changes the nature of this command. This is not an important mitzvah in and of itself, but rather despite the other things being done for the sake of indicating chipazon, one should not injure oneself. A similar aspect in terms of not eating the korban Pesach raw.

I wonder what he would say about those who injure themselves eating large quantities of horseradish, for the sake of the mitzvah...