A brief examination of the 14 rules used by Maimonides as criteria in compiling his list of the 613 mitzvos
“Hermeneutics” refers to the art of biblical interpretation. The 13 Rules of Rabbi Yishmael for expounding the Torah, recited every morning as part of the preliminary service, are often called the “hermeneutical laws.” Other Talmudic sages had lists with more such laws or fewer (Hillel had seven rules; Rabbi Eliezer b. R. Yossi HaGalili had 32), but they’re really dividing the same pie into a different number of slices. Among the hermeneutical processes are such devices as the “kal v’chomer” (a logical inference, such as that a person who can lift 100 pounds can certainly lift 50 pounds) and the “gezeira shava” (a tradition of significance between the same word used in different contexts).
Some laws derived by use of these hermeneutics are biblical, while others are rabbinic. (The former are textual supports to received traditions, while the latter may be outright enactments.) As with the rabbinic “mitzvos” such as reading the Megillah (as discussed in Principle #1), some earlier scholars may have erred by overcompensating, leading to the inclusion in their lists of things that are not truly among the 613 mitzvos.
The Rambam gives an example: Pesachim 22b discusses the possibility that every occurrence of the word “es” in the Torah may come to include something. Rabbi Akiva says that in Deut. 6:13 (“es the Lord your God you shall revere”), the seemingly superfluous word includes the obligation to show proper deference to Torah scholars. However, the Rambam tells us, the obligation to respect scholars is not one of the 613 mitzvos. Similarly, the extra word “es” in Exodus 20:12 (“Honor es your father and es your mother”) may include one’s husband, older brother or step-mother (as per Kesubos 103a), but they are not separate mitzvos.
If one were to include all the laws derived from hermeneutics, the mitzvos would number in the thousands! And it makes no difference if Moshe himself was the one who expounded the interpretation. The Rambam cites the Talmud in Temurah (16a) that 1,700 such expositions were forgotten during the mourning period following Moshe’s death. (No doubt there were many, many more such lessons taught by the Lawgiver that were not forgotten!)
And so, laws derived by exposition, even though they may be biblical, are not necessarily among the 613 mitzvos. The only such things that might be included are those that were part of a received tradition, for which the exegesis is merely a support, rather than the source of a practice.