Knowing It When You See It

Lev. 20:25-26:

כה והבדלתם בין הבהמה הטהרה, לטמאה, ובין העוף הטמא, לטהר; ולא תשקצו את נפשתיכם בבהמה ובעוף, ובכל אשר תרמש האדמה, אשר הבדלתי לכם, לטמא. כו והייתם לי קדשים, כי קדוש אני יהוה; ואבדל אתכם מן העמים, להיות לי.

25 Ye shall therefore separate between the clean beast and the unclean, and between the unclean fowl and the clean; and ye shall not make your souls detestable by beast, or by fowl, or by any thing wherewith the ground teemeth, which I have set apart for you to hold unclean. 26 And ye shall be holy unto Me; for I the LORD am holy, and have set you apart from the peoples, that ye should be Mine.

The Torah uses the same word in two adjacent verses for two different purposes. We must distinguish (והבדלתם) between kosher and non-kosher animals, and God will distinguish (ואבדל) between us and the nations. If I recall correctly, R. Avigdor Nebenzahl, in his published lectures on Parashas Bo, explains that this is a general rule regarding distinguishing, that making proper evaluations according to the Torah is never simple.

The Sifra (10:12) explains that distinguishing between a kosher and a non-kosher animal refers to being able to differentiate between an animal that had more than one and a half of its simanim slaughtered and one that had exactly one and a half cut. As the midrash states, it is a matter of a hairsbreadth. R. Nebenzahl explains that this is the case in general. Thus, the different between chametz and matzah is a matter of seconds, if not less.

Knowing the difference between what is right and what is not, what is kosher and what is not, is a matter that requires great expertise. You don't "know it when you see it." You might know what is not the practice in your community by sight, but that doesn't mean that other practices are improper. It takes great expertise and care to evaluate situations properly and make determinations that are precise.