In Maimonides' introduction to the Sefer Hamitzvot ("The Book of Commandments"), he states the goal he set to accomplish with authoring this work.
The Talmud (end of Tractate Makkot) tells us that there are 613 biblical precepts—248 of which are "positive commandments," i.e., mitzvot that require an action on our part, and 365 "negative commandments," i.e., prohibitions. The 248 positive commandments correspond to the 248 limbs in the human body, each limb, as it were, demanding the observance of one commandment. The 365 negative commandments correspond to the 365 days of the solar year, each day enjoining us not to transgress a certain prohibition.
While the Talmud gives us these precise numbers, it does not list the 248 positive commandments or the 365 negative ones. Thus, numerous "mitzvah counters" have arisen throughout the generations – many who preceded Maimonides – each one attempting to provide a comprehensive listing of the mitzvot, each one's list differing slightly from all others'.
Maimonides prefaces his Sefer Hamitzvot with fourteen guiding principles that allow us to determine which Torah precepts are included in the count, and which are not. He then references these principles throughout the work, and thus arrives at precisely 248 positive commandments and 365 negative ones.
Maimonides explains in his introduction that the objective of the Sefer Hamitzvot is not to explain or elaborate upon the commandments. In an instance where he does speak about the details of a particular mitzvah, the intention is simply to identify which mitzvah he is referring to. The only goal of this work is to enumerate the biblical commandments and to provide explanation as to why certain precepts are counted while others are not.
The following are the fourteen principles (they will be explained at length in the following chapter):
- Do not count Rabbinic Commandments in this list.
- Do not include laws which are derived from one of the Thirteen Principles of Torah Exegesis.
- Do not count mitzvot which are not binding on all generations.
- We do not include "encompassing" directives in the count.
- The reason for a mitzvah is not counted on its own.
- A mitzvah that has both negative and positive components is counted as two.
- The different applications of a mitzvah are not individually counted.
- Do not count a negative statement amongst the prohibitions.
- Do not count the number of times a commandment is mentioned in the Torah, only the act which is prohibited or commanded.
- Do not count a preparatory act as an independent mitzvah.
- If a mitzvah is comprised of a number of elements, do not count them separately.
- When commanded to do a certain action, do not count each part of the action separately.
- We do not count the amount of days a mitzvah is performed.
- We do not count the punishment administered for each transgression.