|Warren Buffet buying chametz|
There are neo-Karaites in our midst. They shun leniencies which have been developed by Rishonim and Acharonim based on interpretations of gemaras, because they say such leniencies do not reflect the original intent of the Biblical law, or of the Biblical law as envisioned by Chazal. Thus, they save, shaving with an electric shaver is a corruption of this original intent; as is using an eruv to carry on Shabbos; as is selling your chametz for Pesach.
One way I like to counter such a position is by turning neo-Karaite myself. You want the peshat? You can't handle the peshat! The peshat in the pesukim is nothing like you imagine. However, Chazal give us midrash halacha. And once you are willing to live and die by Chazal, hem amru ve'hem amru. If by the same halachic principles a ha'arama (legitimate halachic "trickery") is available such that you are working within the bounds of halacha; and sociologically, there is an ethic by which the approach fulfills halachic principles, then please stop complaining.
To focus on selling chametz:
According to the simple peshat in the pesukim, there is no prohibition of owning chametz (leavened bread) on Pesach. There is possibly a prohibition of owning sourdough (se'or), which is used to manufacture chametz. And there is a prohibition of eating chametz on Pesach.
Let us examine the pesukim:
שמות פרק יב
The pasuk above states that you should eat unleavened bread for seven days. Therefore, from the first day, אַךְ בַּיּוֹם הָרִאשׁוֹן -- which means the actual first of the seven days, rather than the midrashic day before Pesach -- sourdough, שְּׂאֹר, used in the manufacture of chametz, leavened bread, shall take a rest, תַּשְׁבִּיתוּ , from being used in your houses, מִבָּתֵּיכֶם. Why shouldn't you be using that sourdough to make chametz? כִּי כָּל-אֹכֵל חָמֵץ, for anyone who eats chametz, leavened bread, during those seven days, from the first to the seventh day, וְנִכְרְתָה, shall be cut off.
[Update: Sorry, I should have been more precise. What I mean by תַּשְׁבִּיתוּ is that you shall cause it to rest. This is how I intended it, but not how I wrote it. Better? :) ]
So it is a prohibition on eating chametz and using, or perhaps owning, sourdough. I would say "using", meaning that there is no reason to use sourdough, since you will not be eating chametz.
A few pesukim later, the same idea is repeated:
שמות פרק יב
For seven days, if one were to look for sourdough, שְׂאֹר, in your houses, it would not be found, לֹא יִמָּצֵא בְּבָתֵּיכֶם. Perhaps this is idiomatic, or perhaps it is the actual definition of the prohibition above of תַּשְׁבִּיתוּ. Why wouldn't it be found? Because the only use for it is to make chametz, which one is prohibited to eat. Thus, what is the reason it would be found? כִּי, because, whoever eats something that has leavened, כָּל-אֹכֵל מַחְמֶצֶת, he shall be cut off, וְנִכְרְתָה. Don't think that machmetzet somehow means se'or, sourdough, on the level of peshat. The word machmetzet means anything that has become chametz, just as the pashtan Ibn Ezra says on this pasuk:
שאור -שהוא מחמיץ והוא הידוע. ואחר כן אמר: כל אוכל מחמצת כל דבר שיחמץ.
ודע כי מיום הראשון עד יום השביעי אינו דבק בקרוב אליו שהוא ונכרתה רק עם אוכל מחמצת, כמו: למלוך שלמה על ישראל.
People don't eat sourdough, for it is not ra'uy le'achila. As Rashi says, citing Mechilta and Beitza 7b, אלא שלא תאמר חמץ שראוי לאכילה ענש עליו שאור שאינו ראוי לאכילה לא יענש עליו. See from here that is not fit for eating, so on the peshat level, the Torah wouldn't bother to forbid it. Plus, we have the earlier pasuk to show us the relationship between the seor to own and the chametz to eat. The same is true here.
שמות פרק יג
In pasuk 13:3, we are command not to each chametz.
In pasuk 13:7, this all falls apart. Because it states that neither chametz nor sourdough shall be seen. Doesn't this then introduce a prohibition on owning chametz, and contradict everything that was specified above?
No, it is describing the same state of affairs as above. You aren't consuming chametz, so you would not be producing chametz. Thus, it is a time for matzah, such that chametz and se'or are not going to be seen in use throughout the Jewish community and the borders of Israel, which is בְּכָל-גְּבֻלֶךָ. This is not the same as the earlier מִבָּתֵּיכֶם, which might convey ownership. This is not a new prohibition on ownership of chametz (or se'or) in the boundaries of your personal property. It is describing the lack-of-chametz-consumption-and-creation within the boundaries of Eretz Yisrael, in line with the mitzvot established earlier on.
So let us say we wanted to be Karaites, and we sold our chametz. Did we use sourdough (or yeast) to make chametz on Pesach? Did we eat chametz? Does anyone own sourdough nowadays? From the letter and spirit of the law, we are fine.
Now, we follow the Oral Law. That means we interpret the pesukim in accordance with the midrash halacha, and so owning chametz and eating se'or are now Biblically prohibited.
But the same Oral Law that sets up a prohibition of owning chametz also defines ownership. The Mishna in Pesachim talks about how one can sell to a non-Jew.
ב,א כל שעה שהוא מותר לאכול--מאכיל לבהמה לחיה ולעופות, ומוכרו לנוכרי, ומותר בהנאתו
They may have envisioned the non-Jew taking physical possession.
Another Mishna states that chametz in possession of a non-Jew is permitted after Pesach:
ב,ב חמץ של נוכרי שעבר עליו הפסח, מותר בהנאה;
Though this was not (necessarily) envisioning a sale from a Jew first.
And another Mishna talks about a non-Jew taking the chametz as a mashkon, a pledge for a loan, or a Jew taking it as a mashkon for a loan:
ב,ג נוכרי שהלווה את ישראל על חמצו, לאחר הפסח מותר בהנאה; וישראל שהלווה את הנוכרי על חמצו, לאחר הפסח אסור בהנאה. חמץ שנפלה עליו מפולת, הרי הוא כמבוער; רבן גמליאל אומר, כל שאין הכלב יכול לחפש אחריו.
The correct interpretation of this Mishna is that if it the chametz is a pledge from the Jew for the loan and then the Jew fails to repay the money, the pledge has belonged to the non-Jew from the time the Jew gave it over, and so the chametz is permitted in benefit. And in the reverse situation, where the non-Jew gave the chametz as a pledge and failed to repay, the Jew was in both physical and legal possession of the chametz throughout Pesach, and so the chametz in prohibited in benefit, for something wrong was done by the Jew.
But one can envision that if the chametz was in the Jew's physical possession but not legal possession, then nothing was technically violated.
Finally, if something will physically remove your ability from accessing the chametz, it is as if destroyed. Think about this and see how it is somewhat significant.
There is also this Tosefta in the second perek of Pesachim, allowing for the "temporary" sale of chametz to a non-Jew:
ב,ו נכרי שבא לביתו של ישראל [וחמץ] בידו אין זקוק לבער הפקידו אצלו חייב לבער ייחד לו בית בפני עצמו אין זקוק לו ישראל ונכרי שהיו באין בספינה וחמץ ביד ישראל ה"ז מוכרו לנכרי ונותנו במתנה וחוזר ולוקח ממנו [לאחר] הפסח ובלבד שיתנו לו במתנה גמורה.
“A Jew and a non-Jew who are on a ship and the Jew has chametz in his possession. The Jew should sell it or give it as a present to the non-Jew and then take it back after the Passover with the stipulation that it be given as a real gift.”
Chazal elsewhere say that bittul be'alma sagi, mere nullification is enough. This nullification is either declaring it hefker, ownerless, according to some, and according to others, distancing it from your mind, such that you do not consider it anything more than the dust of the earth. The latter interpretation is (IMHO) the correct one. Thus, small amounts of chametz in a wall or in a vessel are nullified.
And this "technical" bittul is sufficient. However, perhaps as a fulfillment of one interpretation of tashbitu or as a geder to prevent you from finding a tasty loaf (gluska yefifya) and then taking possession of it, or perhaps as a geder to prevent you from eating it, you are supposed to search out the chametz and dispose of it.
Due to historical developments, the practice of selling chametz arose. People who owned massive amounts of whiskey would no longer have to dispose of their entire inventory at a loss before each Pesach. They could sell it to a non-Jew. And it worked, even though it was perhaps a haarama, that is, halachic 'trickery'. Just like the Talmud allows or recommends halachic loopholes in other situations, such as bringing produce into the house through the window or roof so as to exempt it from terumah and maaser.
Then, the practice spread, and people sold chametz which were part of the ingredients of a larger mixture, or even sold chametz gamur. And maybe some would say that this is a mere ritual, and the people don't really believe it is a real sale. And this is not in such dire circumstances as the ones which prompted the initial permit to sell whiskey. This may not be the same circumstances in which the various Rishonim and Acharonim allowed one to sell chametz. (See here for a better discussion of the history of it.)
Big deal. Society changed, from the time of the Rishonim and early Acharonim. Baruch Hashem, most Jews do not stock their pantries with the bare minimum of food, which is all we can afford, and which could (in all instances) be easily finished before Pesach. We have full shelves, and refrigerators, and freezers. Halacha and its application develops over time, and now it is an accepted practice in some communities. Just as the Rishonim worked within the bounds of the halachic system to allow for a changed situation that was common in medieval Europe, later Acharonim (see e.g. the Chasam Sofer) worked within the bounds of the halachic system to allow for our changed situation.
Meanwhile, what do people do? They fence off their chametz, by placing them in specific cupboards and taping those shut. Biblically, there is no sourdough to speak of; the chametz cannot be "seen" (though even this is an overly literal requirement), and the chametz is not going to be eaten. From a peshat perspective, the letter and spirit of the law is being fulfilled.
From a halachic perspective, the letter of the law is fulfilled by these machinations. And haarama is not cheating, but is part of the same halachic system. Don't be an inconsistent Karaite, by accepting Chazal's interpretation of the pesukim and rejecting the idea of haarama. The spirit of the law is also fulfilled, as described above. And just like bittul by itself is sufficient, because of technical rules and because one is removing his mind from the possibility of eating it, so does technically selling it remove from one's mind the possibility of eating it. And the geder against coming to eat chametz is also fulfilled. Since the people know that the chametz is not theirs, and they physically cut off their access to it, they will not come to eat it.