How illogical is halakha? At first blush, one would say, not very. Halakha is, almost by its very definition, logical. And certainly that was the original intent. Even laws that had no understandable reason, like shatnez, were handled by halakha in a largely logical fashion. But today one can see halakha’s original intent corrupted.
A case in point: many of the laws governing sex – and by this I do not mean biblical laws like the ban on male-male anal intercourse – have been twisted into a hardened, restrictive shell. The source for this increasingly restrictive halakha? The Zohar, that wonderful 13th century forgery beloved by hasidim, haredim and Sefardim alike. The idea that a male spilling seed is a worse sin than murder? That’s right. You can trace that line of "reasoning" directly back to Rabbi Moshe DeLeon’s creative writing project.
No serious scholar believes the Zohar is authentic; indeed, even most rabbis hold large parts of the "text" were added over centuries by various authors and is itself corrupted.
But, just for a moment, let’s put aside fact and instead accept, just for the sake of argument, the "authenticity" of the Zohar. Now, let’s ask a question: Can the Zohar be used to decide halakha?
The Zohar was "concealed" for more than 1000 years. During that time, the Mishna was redacted, as as the Talmud. Geonic codes were written. Rashi lived and wrote. Dozens of halakhic works were written and published and responsa literature flourished. All of these were written without knowledge of the Zohar.
Then, just before the turn of the 14th century, the Zohar is "discovered" by a lone rabbi who brings no verifiable proof for its authenticity. Should halakha take the Zohar’s views into account? Should it become more strict on the Zohar’s account?
Logic and fair play would say no. Unfortunately, rabbis said yes. Why did they do so? Rabbis adopted the Zohar as a quasi-halakhic text largely because of three men and their disciples: Shabbatai Zevi, The Ari, and the Ba’al Shem Tov.
The Ari lived almost 300 years after the "discovery" of the Zohar, and
the Ari made the Zohar the cornerstone of his theology. He decided law
like the Zohar and gave out mystical "tikkunim" based on it. (One of
these tikkunim was quite popular among his disciples. It was used to
cleanse onesself of the "impurity" caused by spilling seed. Another
very popular one did the same for homosexual relations.) He taught for
a very brief time and then died young in his thirties. His disciples –
a handfull of students, no more – spread his teaching across the Jewish
world. But those teachings remained non-normative until the appearance
of Shabbatai Zevi.
Shabbatai Zevi, the most influential false messiah Judaism had until the end of the 20th century, was followed by most of the world’s rabbis, and Shabbatai not only used the Zohar as a halakhic text, he used it to abrogate or radically change existing laws. After his conversion to Islam, most of his rabbi-followers went back to normative halakhic Judaism, but some went back as crypto-Sabbateans. Both groups used the Zohar as if it were halakha, and their influence was widely felt.
Indeed, the founder of the hasidic movement, the Ba’al Shem Tov came into prominence in an area of Europe that was a hotbed of both open Sabbateanism and of its crypto variety. His disciples elevated the Zohar to near-biblical status, and incorporated its views of sexual issues and ritual purity, codifying them as "halakha," and relying on crypto-Sabbatean works for guidance.
So, back to our question: Can a book of questionable provenience be inserted into halakhic discourse after more than 1000 years and with no contemporaneous mention of it in halakhic sources of the time of it’s alleged authorship by Shimon Bar Yohai?
Logic, honesty and fair play would clearly say no, it cannot be used as a source of halakha and can play no role in halakha. Instead, the exact opposite has happened. Rabbis opted for the Zohar’s strictness, and in the process threw logic and fair play out the window.
Jews deserve better than halakha based on this 13th century "find." Too bad our rabbis did not and do not understand this.