Generally speaking, the mitzvot are divided into two categories: logical mishpatim ("laws" or "judgements") and supra-rational chukkim ("decrees").
The mishpatim are mitzvot such as the commandment to give charity or the prohibitions against theft and murder, whose reason and utility are obvious to us, and which we would arguably have instituted on our own if G-d had not commanded them. The chukkim are those mitzvot, such as the dietary laws or the laws of family purity, which we accept as divine decrees, despite their incomprehensibility and -- in the most extreme of chukkim -- their irrationality.
[A third category, the eidot ("testimonials"), occupies the middle ground between the decrees and the laws. A testimonial is a mitzvah which commemorates or represents something -- e.g., the commandments to put on tefillin, rest on Shabbat, or eat matzah on Passover. These are laws which we would not have devised on our own, certainly not in the exact manner in which the Torah commands; nevertheless, they are rational acts. Once their significance is explained to us, we can appreciate their import and utility.]
Yet each of these terms -- mishpatim, chukkim and eidot -- is also used by the Torah as a synonym for "mitzvah" and a reference to all commandments of the Torah. A case in point is the Torah section of Mishpatim (Exodus 21-24), which opens with G-ds words to Moses, "And these are the mishpatim that you shall set before them." The 53 mitzvot that follow are indeed primarily logical laws, but they also include a number of "testimonials" and at least one supra-rational "decree" -- the last mitzvah in the series, which is the prohibition against mixing meat with milk ("Do not cook a kid in its mother's milk").
Chassidic teaching explains that every mitzvah is, in essence, a supra-rational chok, and at the same time, every mitzvah is also a comprehensible mishpat.
G-d created the human mind and the logic by which it operates. Obviously, then, it would be nothing less than ridiculous to assume that G-d desires something because it is logical. Rather, the reverse is true: something is logical because G-d desires it. In other words, the reason the commandment "Do not kill" is logical to us is that G-d desired a world in which life is sacred, and molded our minds in accordance with His vision of reality. In essence, however, "Do not kill" is no more logical than the mitzvah of parah adumah (the commandment to sprinkle the ashes of the Red Heifer upon someone who has been ritually contaminated through contact with a corpse -- often cited as the ultimate chok). So the rationality of the commandment "Do not kill" is but an external "garment" behind which lies the mitzvah's essential nature as the supra-rational will of G-d.
In the words of the Tanya: "The rationales of the mitzvot have not been revealed, for they are beyond reason and understanding. Also in those instances in which there has been revealed and explained a certain reason which is apparently comprehensible to us, this is not ... the ultimate reason, for within it is contained an inner, sublime wisdom that is beyond reason and understanding."
On the other hand, even the most irrational decree has its rational elements that can be analyzed by the human mind and appreciated by it as a lesson in life. As Maimonides writes, "Although all the chukkim of the Torah are supra-rational decrees... it is fitting to contemplate them, and whatever can be explained, should be explained."
Thus, every mitzvah -- whether categorized as a chok or a mishpat -- is basically a supra-rational decree which can nevertheless be experienced as an illuminating guide to life. Every mitzvah is an act of submission to the divine will, an act that recognizes that our finite minds cannot fathom the axioms that are the basis of our reality and must ultimately accept them on faith from their divine conceiver. At the same time, every mitzvah is a rational act in the sense that it relates to our rational selves and aids us to achieve a better understanding of our nature and our purpose in life.
The only difference between chukkim and mishpatim is: which of these two elements dominates. The chok emphasizes the supra-rationality of our commitment to G-d, while the mishpat stresses the function of the mitzvot as educators and enlighteners of human life.
The Wise Son Asks
This is the deeper significance of the question posed by the "Wise Son" in the Haggadah, "What are the eidot, chukkim and mishpatim that G-d commanded you?" Why the need for different types of mitzvot, the Wise Son is asking, characterized by varying degrees of rationality? What can be more significant and more meaningful than the simple fact that one fulfills a Divine command?
To answer the Wise Son's question, the Haggadah says to "tell him the procedures of the Passover offering, [including the law that] after eating the Passover offering, one may not conclude the meal with a dessert."
Passover, so named after G-d's passing over all norms to redeem His people, represents the transcendence of the natural and the reasonable in our relationship with G-d. But Passover, too, has its "procedures." Also the loftiest, most supra-rational truths are to be incorporated into our natural existence -- an existence characterized by logical laws and rational processes. Indeed -- we continue to explain to the Wise Son -- the law is that, "After eating the Passover offering, one may not conclude the meal with a dessert," in order that the taste of the Passover offering should linger in our mouths. Also the reason-transcending Passover aspect of our relationship with G-d should impart a taste -- an intellectual and emotional savor -- to the palate of the soul.
This is why the Torah includes decrees, testimonials and laws. For though it is in essence a divine decree, it is to be experienced as a program for life that addresses our every plane of being, from its technical-logical aspects to our capacity to abnegate reason in subservience to the divine will. Furthermore, not only does the Torah include both chukkim and mishpatim, but also its most supra-rational decree can, and should, be assimilated by our thinking and feeling selves as a source of enlightenment and feeling.
Axiom or Instrument?
In addition to the distinction between supra-rational chukkim and rational mishpatim, these two facets of the mitzvah -- the mitzvah as divine decree and as a program for life -- are also expressed in other divisions and categorizations of the mitzvot.
For example, the law states:
If a Jew is forced to either transgress any of the mitzvot commanded by the Torah or else be killed, he should transgress rather than be killed. For regarding the mitzvot, it is written, "[You shall keep My chukkim and mishpatim,] which man should do and live by them" -- live by them and not die by them... When does the above apply? In regard to all mitzvot, except for [the prohibitions against] idolatry, [certain] sexual sins, and murder. Regarding these three transgressions, if a person is told to either commit one of them or else be killed, he should be killed rather than transgress. (Mishneh Torah, Laws of the Fundamentals of Torah, 5:1-2).
Why this distinction between mitzvot? If the mitzvot exist to live by rather than to die for, this should apply to all mitzvot. On the other hand, if a person ought to give his life rather than violate the divine will, then this should apply to all mitzvot, since every mitzvah is equally a command of G-d.
Indeed, the mitzvah is both superior to human existence and integral to it. As a divine decree, dictated solely by the infinite and absolute will of G-d, it is greater than life, greater, certainly, than life's finite and equivocal manifestation in a physical body. On the other hand, as illuminator, enhancer and sanctifier of life, the mitzvah is something that comes to serve life, not to supersede it.
When a person is confronted with the choice to violate a mitzvah or die, the two faces of the mitzvah are brought in conflict with each other. The question then is: which element of the mitzvah dominates? Which should give way before the other? In most cases, the "live by them" element of the mitzvah takes precedence. But there are certain mitzvot in which the "divine decree" aspect dominates: what is most significant is that G-d commanded and man must obey, regardless of the consequences to man's ephemeral existence as a physical being.
Another expression of the chuk and mishpat elements within the mitzvot is the distinction between biblical commandments (mitzvot d'oraita) and rabbinical commandments (mitzvot d'rabbanan).
The biblical commandments are the 613 mitzvot explicitly or implicitly contained in the Five Books of Moses. The rabbinical commandments are the laws instituted by sages throughout the generations. (For example, praying three times a day, reciting kaddish after the dead, making a blessing before eating, lighting Shabbat candles, and the festivals of Chanukah and Purim are all rabbinical institutions. Indeed, a major part of what we call "Judaism" is of rabbinic origin.)
Both are equally binding upon the Jew. The sages institute their laws by the divine authority expressed in the verse: "And you shall observe all that they shall instruct you" (Deuteronomy 17:10). Thus, the blessing recited before the performance of a mitzvah -- "Blessed are You, L-rd our G-d, King of the Universe, Who has sanctified us with His commandments and commanded us to..." -- is recited over rabbinical mitzvot as well. G-d is the sole commander of a mitzvah, whether it is written or alluded to in His Torah, or instituted by human beings to whom He imparted the authority to interpret and safeguard His laws and legislate Jewish life.
Nevertheless, Halachah (Torah law) distinguishes between biblical and rabbinical laws, applying a different set of standards to each of the two categories. One of these differences is that, according to many halachic authorities, biblical laws define the nature of their object, while rabbinical degrees are only prohibitions upon the person. For example, if biblical law forbids a certain food, this indicates that the very substance of the food is intrinsically negative and profane; on the other hand, rabbinical proscription of a certain food is strictly a prohibition upon the person not to eat it.
At first glance, this seems to indicate that rabbinical mitzvot are less "real" than biblical ones; that while the biblical law affects the very nature of its subject, the rabbinical law is superimposed over human life, having the authority to command and instruct but not to define reality. On a deeper level, however, this alludes to the fact that the rabbinical law is the more profound expression of the essence of the mitzvah as divine will.
The biblical mitzvot define the nature of our world, expressing the fact that their predominant element is the mitzvah's role as molder and illuminator of the created reality. Not so the rabbinical commandment, which is concerned only with what man should or should not do, not with how this affects him or his world. Thus it asserts the "decree" element of the mitzvah: the mitzvah as it transcends all relation to physical life, its sole purpose being the fulfillment of a divine desire.