"Vay'dabeir Elokim es kol had'varim ha'eileh laimor" -- "And G-d spoke all of these words, saying (Yisro 20:1)." With this verse, the Torah introduces the Decalogue, the 'Aseret HaDib'ros. Rashi, quoting the Midrash, writes that all the commandments were miraculously stated in one utterance by G-d. Commenting on the textual source for this tradition, Rav Yosef Dov Haleivi Soloveitchik zt"l noted that the Hebrew word for all -- "kol" -- has two meanings: 1) the collective aggregate of many units or 2) the totality of an item or concept. Here, Chazal taught, the word "kol" cannot carry the first meaning as that would be obvious; of course, G-d uttered all of the dib'rot following the introductory phrase. Therefore, it must mean the totality of the dib'rot,and hence the tradition that all these commandments were uttered as one whole.
Rav Soloveitchik continued to explain in light of the observation by many of the commentaries that each of the two luchos focuses on different types of mitzvot -- the first on Mitzvot Bein Adam LaMakom, the second on Mitzvot Bein Adam LaChaveiro -- that these two luchot comprise one indivisible entity. Allegiance to one half only is not only a corruption of the Divine message but inevitably leads to disaster. Social Morality, or an ethical system of thought not based on the "I am G-d" legislator of the first tablet, is at best subject to many whimsical, immoral judgments and at worst to self-destruction. The Rav quoted the example of the Soviet Union, which, although founded on a basically "moral" doctrine of Marxism (">From each according to his ability, to each according to his need"), but, being atheistic in its very foundation, inevitably would and did lead to the totalitarian, brutal, murderous state that, under various leaders, the Soviet Union became.
An interesting insight of R. Naftali Zvi Yehuda Berlin (NeTzIV) drives this point home as well. When Avraham is confronted by Avimelech about his trying to pass off his wife as his sister leading to Avimelech almost committing an adulterous affair with her if not for direct Divine intervention, Avimelech states: "For you have brought on my kingdom a great sin (VaYeira 20:9)." We find no parallel statement in the words of Pharaoh when a similar incident occurred with him and Sarah in Parshat Lech Lecha. Pharaoh merely blames (then) Avram for not informing him that she was his wife; he does not mention anything about sin. Apparently, Philistia was a more moral country than Egypt, and as such, Avimelech was concerned about the great transgression involved. This is also evidenced by the fact that after the episode with Pharaoh, Avram is chased out of Egypt to avoid any possible repeat of Sarah being taken away because the Egyptians were immersed in immorality (see Rashi (12:19)). After the incident with Avimelech, Avraham is allowed to stay in Philistia because no such fear existed in light of the moral chastity prevailing in the land. In light of all this, it comes as a surprise when Avraham responds to Avimelech's accusations: "For I said, but there is no fear of G-d in this place, and they will kill me because of my wife (20:11)." Why is Avraham concerned that in such a moral climate, that murder would be considered an alternative? Furthermore, if adulterous acts were not considered reprehensible, why would Avimelech bother killing Avraham instead of just sinning with Sarah? The Netziv answers (in his commentary Ha'amek Davar) that human morality -- no matter how seemingly just, no matter how well-kept and widespread -- is flexible. The creators of the morality can create loopholes at will. It can immediately become moral for a king to take women as he wishes or kill as he wishes. One could even justify this based on "Divine right" or some other catchy phrase bolstering the right of monarchs to rule as they wish. It is this problem that Avraham addresses. In effect, he tells Avimelech: "If your sense of right and wrong is dictated by your own senses -- whether it be based on your logic, your emotions, your drives, or your feelings -- and not based on a G-d given, fixed, rigid, unwavering system of Absolute Right and Wrong, then I can have no confidence in you or your system of laws."
What emerges crystal-clear is that we cannot allow our own feelings or logic to dictate right or wrong. This leads to confusion and disaster. Our only measuring-stick of Right and Wrong must perforce be the Torah, the Revelation of the Divine Will. (See Chazon Ish in his Emunah U'Bitachon for further elaboration on this point.)
Rambam (Hilchos M'lachim) rules conclusively that the Seven Noahide Laws, of which at least three focus on interpersonal laws (murder, theft, adultery), must all be kept as a result of Divine command and not just human reason. This is true even though the interpersonal laws are mishpatim, or mitzvot which Man could have intuited on his own. Nonetheless, the Legislator, the Authority, and the Cause of their binding nature, and the One who determines their scope are all one and the same: G-d Himself. Only one who recognizes this and fulfills them with this truth in mind will receive Eternal Life for adherence to them.
Malbim, in his commentary to Tehillim makes a similar observation. There the Psalmist writes: "He tells His words to Jacob, His statutes (chukav) and His laws (mispatav) to Israel. He did not do so to any [other] nation, and laws (mishpatim) they do not know, praise G-d!" (147:19-20). Noting the difference between "mishpatim" which generally refer to social laws able to be arrived at by human minds and chukim, laws only known by Divine command, Malbim comments on the latter verse, that, not only don't the nations of the world know G-d's chukim, since they were not dictated to them, but even the mishpatim are not kept by the majority of Nations as a result of Divine command and therefore cannot serve as a source of Eternity for them.
In a world of moral relativism, spiritual confusion, and rancorous debates about crucial issues of morality, the Torah continues to serve as the bedrock of Divine Truth waiting for the Jewish people and all of Mankind by extension to drink from its Wisdom to provide guidance and enlighten all of life's dilemmas.