I think that the principle that, "Here it was found, so it is," applies only to when there is a change in domain. I mean to say that it is a principle that tells us about the time some change occurred, but only when there was change in domain.[If there was no change in domain, then hezkat of body would tale precedent] The reason I say this is because there is apparently a contradiction in the Rambam. On one hand, he holds a sota is a doubt. And on the other hand, he holds a bride in her father's house is considered to be in her father's domain [even though she has also become an arusa espoused or engaged]. There she is considered to be definite. That is she is considered to be in her fathers domain definitely not just by a doubt. To make it clear what I am referring to here let me bring the gemara in Ketuboth page 75 and 76. The case is a little complicated. For if a engaged woman was living with her father until marriage. Then she was married, and the husband found her to have blemish. The husband claims that she had a blemish before she was espoused. In that case, the Rambam holds that the wedding was a mistake, and the father must return the money of the marriage. That is, the Rambam holds this a case of a certainty. [If she received the blemish after she was espoused even though she was still in her father’s home, then that is considered to be in the husband's responsibility.] However, the Rambam says that a sota does not eat truma because she is in doubt, and also that her husband cannot live with her because she is in doubt. So to the Rambam, a sota is a doubt. Then why do we say that we learn from sota and from two hazakot that the mikve that was found lacking the right volume is definitely not OK. The reason is because we learn from sota that there is a doubt and the two hazakot makes it definite.] So, we learn that a hazaka of the body pushes the time a change happened to be as late as possible even against a hazaka that something is found now to have a problem. So why then in the case of the bride do we say the change happened as late as possible? After all she might have received the blemish after the espousal? It must be that in the opinion of the Rambam, the principle, ''Here it was found, so here it,'' was applies only to a case when there was a change in the domain and when there was a change in the domain this principle overrides all other hazakot even hekat hagof. --------------------I think that the principle that כאן נמצא כאן היה applies only to when there is a change in domain. I mean to say that it is a principle that tells us about the time some change occurred, but only when there was change in domain. The reason I say this is because there is apparently a contradiction in the רמב’’ם. On one hand he holds a sota is a doubt. And on the other hand he hold a bride in her fathers house is considered to be in her fathers domain even though she has also become an ארוסה espoused or engaged. and there she is considered to be definite. That is, she is considered to be in her fathers domain definitely, not just by a doubt. To make it clear what I am referring to here let me bring the גמרא in כתובות page ע''ה and ע''ו. The case is a little complicated. For if a engaged woman was living with her father until marriage. Then she wasנשאת , and the husband found her to have blemish. The husband claims that she had a blemish before she was espoused. In that case, the רמב’’ם holds that the נישואין was a mistake and the father must return the money of theקידושין . That is the רמב’’ם holds this a case of a certainty. All the husband needs to do is to prove that she had the blemish while she was still living with her father, and then we say that she had the blemish even before he was espoused. [If she received the blemish after she was espoused, even though she was still in her father’s home, then that is considered to be in the husband domain. Even so all the husband needs to do is show by witness that saw her in the bathhouse that she has blemish before the actual wedding, and then we say she had it before the espousal. However, the רמב’’ם says that a סוטה does not eat תרומה because she is in doubt ספק זונה , and also that her husband cannot live with her because she is in doubt ספק זונה . So, to the רמב’’ם, a סוטה is a doubt. Then why do we say that we learn from סוטה and from two חזקות that the מקוה that was found lacking the right volume is definitely not OK. The reason is because we learn from סוטה that there is a doubt and the two חזקות makes it definite.] So, we learn that a חזקת הגוף pushes the time a change happened to be as late as possible even against a חזקת השתא that something is found now to have a problem. So why then in the case of the bride do we say the change happened as late as possible? After all she might have received the blemish after the espousal? It must be that in the opinion of the רמב’’ם the principle כאן נמצא וכאן היה applies only to a case when there was a change in the domain and when there was a change in the domain this principle overrides all other חזקות even חזקת הגוף. After writing the above I saw Rav Shach brings this idea himself [Laws of Trumot, chapter 5, law 24] that the principle, “Here it was found, so here it is,” applies only to a case of change of domain. It is in the Mishnas Reb Aaron that I saw that the Rambam holds this principle intends the case to be definite, not just a doubt. And I saw in Reb Shmuel Rozovski that the Rambam holds a Sota is a doubt. In one place Rav Shach brings the combination of two hazakot and learning from Sota that makes the case of the mikveh to be definite [Pure things made on a mikve that was found lacking the right volume are definitely unclean, whether in a public or private domain.] Later I saw that Rav Shach gives a different answer for the Rambam, i.e. that the Rambam decided the law like the second answer of R Chanina. Also, Rav Shach suggested that the Rambam holds the case of the pure things that were prepared on a mikve that was found to be lacking is in fact a case of doubt. So, there is no contradiction between the case of the barrel and the case of the mikve. Both are a case of doubt.---------------------- Unrelated to the above paragraphs I would like to ask two questions, one on the first statement of ר' חנינא נידה page 2 and3. He says the teaching about the barrel is ר שמעון. But if so, then why does that teaching say nothing about a public domain? I mean to ask, that if it is ר שמעון, then the case of the barrel should say that if one depended on the חבית in a public domain, then the תרומה should be ok. On the other hand, you can ask that this is hard to say that you assume the separation was done right without evidence.) The other question is the last statement of ר' חנינא you learn the end of tuman from the beginning. If so, even in a רשות היחיד the person should be pure since we learn end of טומאה from the beginning. ___________________________________________________________________________________After writing the above I saw רב שך brings this idea himself [Laws of Trumot, chapter 5, law 24] that the principle, “Here it was found, so here it is,” applies only to a case of change of domain. It is in the משנת ר' אהרן that I saw that the רמב''ם holds this principle intends the case to be definite, not just a doubt. And I saw in ר' שמואל רוזובסקי that the רמב’’ם holds a סוטה is a doubt. In one place רב שך brings the combination of two חזקות and learning from סוטה that makes the case of the מקוה הנמדד ונמצא חסר to be definite. [טהרות שנעשו on a מקוה הנמדד ונמצא חסר are definitely טמאות, whether in a רשות הרבים or רשות היחיד.] Later I saw that רב שך gives a different answer for the רמב’’ם, i.e. that the רמב’’ם decided the law like the second answer of ר’ חנינא. Also, רב שך suggested that the רמב’’ם holds the case of the טהרות that were prepared on a מקוה הנמדד ונמצא חסר is in fact a case of doubt. So, there is no contradiction between the case of the חבית and the case of the מקוה הנמדד ונמצא חסר. Both are a case of doubt. Unrelated to the above paragraphs I would like to ask two questions, one on the first statement of ר' חנינא נידה דפים ב' andג' . He says the teaching about the חבית is ר שמעון. But if so, then why does that teaching של חבית say nothing about a רשות הרבים? I mean to ask, that if it is ר שמעון, then the case of the חבית should say that if one depended on the חבית in a public domain, then the תרומה should be ok. On the other hand, you can ask that this is hard to say that you assume the separation was done right without evidence.) The other question is the last statement of ר' חנינא you learn the end of טומאה from the beginning. If so, even in a רשות היחיד ,the person should be טהור since we learn end of טומאה from the beginning.