Rabbis believe they have a right to make biblical observance stricter. That approach presumes they know the divine intention and can further it. The implicit presumption that they can lay down the laws better than God did is absurd. It is also a carbon copy of the Conservative Movement’s doctrine, which the Orthodox establishment detests: the Conservatives imagine they can abrogate a commandment if they see a rationale for it and if that rationale would lead to a different conclusion if applied now.
When a government sets the speed limit at 65mph, would we presume to drive 40mph max to show our respect for the current president? The commandments similarly strike a balance between different objectives, such as freedom and holiness; any attempt to make them stricter breaks the entire system apart.

Stricter does not mean better. Rather, it often means abrogation. The rabbis virtually eliminated the Torah’s punishments by erecting impossible rules of evidence. An unruly son cannot be condemned because his parents cannot accuse him “in a single pitch of voice” as the rabbis demand. Even mundane murderers cannot be punished because all the circumstantial evidence is rejected: the rabbis need two people who witnessed the murder, which is clearly an impossible requirement in many situations. In Tanakhic times, Jew freely brought sacrifices when the Temple was not available; by making the rules of sacrifices stricter, rabbis prevent us from bringing them even though we must. The red heifer, an animal so common in antiquity that its ashes were available in every village, has by now acquired impossible qualities: the heifer was required to have no more than two hairs of another color; in consequence, all Jews persevere in a state of ritual impurity.

Or, take the de facto marriage. Isaac married Rivkah simply by “taking her in his mother’s tent.” She now lived with the clan’s women, and that was it. No conversion (she had been pagan) or rabbinical marriage. The Torah offers full support for de facto marital relations: if an unmarried couple has relations, they only need to marry to avoid a death sentence. Thus, the Torah explicitly sanctions pre-marital relations. Now, we might guess whether the lawgiver lauded such relations. Monarchy and slavery are similarly allowed, though frowned upon and heavily restricted.

God’s reasoning, however, is not our business. A wise midrash tells us that when Hebrews enthusiastically accepted the law on Sinai, God hanged the mountain above them and demanded that they accept it out of fear. Sages prohibited us from extolling the law as merciful—for oftentimes it is not. Once we tread on the sleazy slope of rationalizing commandments, we cannot avoid the rabbinical trap of setting ourselves above the Torah. Indeed, we’re better than the one whose reasoning we understand, because besides his knowledge we also have our own knowledge.

A refusal to analyze the Torah is really insulting; we’re used to analyzing everything. Or do we? Where does the aesthetic rule of eating with knife and fork come from? In fact, we take the majority of laws for granted without questioning them. Moreover, we can try analyzing the Torah, but never to change it. The principles which we imagine in it can guide us in developing secular law. The Torah is silent on charity to urban dwellers, for example. But whatever is laid down clearly in the Torah is not for us to bind or loose.