Rabbi Hershel Schachter
The posuk in Parshas Shoftim uses three different phrases to describe a disagreement about halachah - "bein dama l'dam, bein din l'din, bein negah l'negah" (17:8). The Vilna Gaon is quoted in the Sefer Aderes Eliyahu as having commented that this language indicates that all the dinim of the Torah are classified into three distinct categories: issur v'heter, dinei mamonus, and tuma v'tahara. The parsha states that if in any one of these three areas there is a machlokes among the chachomim in town which is ripping apart the community, the issue must be presented to the Sanhedrin in Yerushalayim which should give the psak that will be binding on all of Klal Yisroel. The implication is that were it not for the fact that the machlokes among the rabbonim is causing friction and ripping apart the community, each group would follow their own poseik.
The Tosefta (Sanhedrin 7:5) tells us that all the laws of the Torah are interconnected and fall into one big pattern to comprise one big mosaic. The Gemarah will, therefore, often learn out the details of one mitzvah from another mitzvah. Nonetheless, the Gemarah does put limitations upon this concept of all of Torah fitting into a single pattern. The Gemarah says that issur v'heter cannot be learned out neither from tumah v'taharah (Yevamos 103b) nor from dinei mamonus (Berachos 19b). These sources seem to be implying that each one of the three areas of halacha makes up its own pattern; all of dinei mamonus fit into one pattern, all of the laws of issur v'heter fall into a separate pattern, etc. (see Sefer Eretz Hatzvi siman 2).
When we are in doubt as to what the facts of a case are, the halacha has a different way of resolving the safeik depending on which category of dinim the case at hand belongs to. Regarding issur v'heter, we assume that any safeik regarding a din min ha'Torah must be resolved l'chumrah. However, when we have a safeik in the area of dinei mamonus the psak will be in favor of the muchzok (possession is nine-tenths of the law) which is l'kula. Finally, when the safeik is in the area of tunah v'tahara, whether the psak will be l'hachmir or l'hokeil will depend on the location where the safeik arose - in a reshus ha'yochid or in a reshus ha'rabim.
In addition to these three areas of halacha, the Gemarah tells us that there are another three areas that are treated differently. With respect to dinei n'foshos the Torah tells us "V'he'tzulu ha'aida" (Bamidbar 35:25), i.e. we should always bend over backwards to try to acquit the person being judged, and this applies even with respect to the way we darshan the halachos by reading in between the lines (Sanhedrin 69a). In the area of avoda zara the Torah tells us "shakeitz t'shaktzenu", etc., which implies that we should always bend over backwards to go l'chumrah when darshening the pessukim, and in the area of kodshim, the Gemarah (Zevochim 49-50) discusses at length the fact that the middos she'haTorah nidreshes bohem apply differently to kodshim from how they apply to the rest of the Torah regarding lomeid min ha'lomeid (learning out C from B where B itself was derived from A).
Reb Yehuda Ha'Nasi edited the mishnayos and divided everything into six sections. The sedorim of Nezikin, Kodshim and Taharos constitute three separate areas of halacha.
Some are only careful in observing those mitzvos which are bein adam laMakom and not that meticulous in nezikin (bein adam lachaveiro). Others are only extremely careful in observing those mitzvos which are bein adam lachaveiro while not being that meticulous in observing those mitzvos in the area of issur v'heter (bein adam laMakom). An Orthodox Jew is one who is equally meticulous in all areas.
It is quoted in the name of the Vilna Gaon that many divide all mitzvos into two categories: bein adam laMakom and bein adam lachaveiro. In reality, there is a third category: bein adam l'atzmo. We have the mitzva of V'holachto b'derachav - to preserve the tzelem ELokim that was implanted within us at birth by developing our middos. The Gemarah (Bava Kamma 30a) tells us that one who wishes to become a chassid should be meticulous in three areas of halacha - avos, nezikin, and berachos. These three represent the three areas of mitzvos - bein adam laMakom, bein adam lachaveiro, and bein adam l'atzmo.
Unfortunately many people are only selectively observant. Listed among the various mumin (wounds or blemishes) that invalidate a kohein from being markiv korbanos in the Beis Hamikdash is saru'ah, one whose limbs are not symmetrical (e.g. one arm is noticeably longer than the other, one eye is noticeably larger than the other.) I remember Rav Nissan Alpert's hesped at the funeral of Hagaon Rav Moshe Feinstein wherein he mentioned that he met many gedolim in his lifetime whom he felt that suffered, in a certain sense, from the mum of saru'ah. Some were very meticulous in one area of halacha, but not to the same extent in other areas. And some were especially strong in learning in one area of Torah (psak halacha, Kodshim, Nashim & Nezikin, etc.) but not equally as strong in all other areas of Torah. The one and only gadol b'Torah he knew who seemed to be equally strong in all areas of Torah and equally meticulous in all areas of miztvos at the same time was his rebbe - Hagaon Rav Moshe Feinstein.