Thursday, January 26, 2017

Matrilineal Descent

Halacha and the frum world take it for granted that whether a person is born Jewish is determined by whether he or she had a Jewish mother. It is assumed that the principle of matrilineal descent goes back as far as there have been Torah-abiding Jewish people.[1] Yet we see in Tanach many examples of Jewish men marrying non-Jewish women. Yosef marries an Egyptian, Moshe a Mdianite, David a Pilishti, and so on. Their children are all considered Jewish. There is an assumption that these women were migayar, and in the case of Yosef and Osnas, a medrash that claims she was really Jewish all along, but there is no indication of this in the pesukim. There is also some indication in Tanach that a woman who married a non-Jewish man was then considered part of his nation, and their children were not Jewish.

The principle of matrilineal descent doesn't appear in any extra-biblical sources, either. Writers such as Philo of Alexandria and Josephus seem unaware of it, as do the Dead Sea scrolls and various early works which survive but were not canonized as part of Tanach. The earliest recorded instance of the principle of matrilineal descent seems to be in the mishnah.

The Mishnah in Kiddushin 3:12 discusses potential valid and invalid marriages, and states that in a halachically valid marriage, the status of the children is that of the father, i.e., whether the children are cohanim or not. When the marriage is invalid, the children are hallachically fatherless, and follow the status of the mother. A marriage between a Jew and non-Jew in not hallachically valid, so the children's Jewish status depends upon their mother's Jewish or non-Jewish status.
Under Roman law, a child is legally his father's heir only if he is the product of a valid legal marriage. Marriages recognized by the law were restricted to unions between Roman citizens. If a citizen married a non-citizen, the children followed the status of the mother. A Roman father and a non-Roman mother produced non-Roman children. A Roman mother and non-Roman father would theoretically produce Roman children, but a separate, later law dictated that the children follow the parent with the lower status.

The logic is identical to that found in the Mishnah. The Mishnah developed during the period when Judea was ruled by Rome. It seems more likely that the law of the powerful Roman Empire, which was legally binding throughout the empire,  influenced Jewish jurors in the Roman province of Judea in the first centuries CE than that a hitherto unattested law from the backwater kingdom of Judah influenced Roman jurors hundreds of years earlier.[2] It is likely, then, that matrilineal descent, the method by which we determine who is Jewish, is originally not a Torah principle but a Roman one. That something so fundamental to Jewish identity could have originated in another culture undermines the idea that Judaism as practiced today in the frum world is essentially the same as it has been down through the ages.

[1] The following discussion of matrilineal descent is based on Cohen, S.J.D. (2001). The Matrilineal Principle in Historical Perspective. AJS Review. Retrieved from
[2] The author of the article provides another suggestion for the origin of matrilineal descent. He says that it may be part of the mishnah's fascination with categorizing things, and points to a discussion of kilayim, an animal such as a mule which is the offspring of two species. There is an opinion there that the species of the animal follows the mother, and so too, the author suggests, in cases of two nationalities the child follows the mother. I would suggest that it is more likely that his first explanation is correct, and matrilineal descent was borrowed from Roman law. The logic of the Roman law and of the Mishnah is identical, and given the historical timing of the Mishnah is probably not a coincidence. If so, then the principle of matrilineal descent with regard to children may have been applied to cases of kilayim, rather than the other way around.

Tuesday, January 24, 2017

Confidence and Illusory Reliability

In The Invisible Gorilla[1] the authors discuss various cognitive biases or typical errors in thinking they have found in their psychological research. Among them is the illusion of competence created by an air of confidence. They relate an incident in which one of them discovered a rash on his leg and went to see a doctor. The doctor looked through a book on skin rashes to reach a diagnosis, and then consulted another book for the appropriate treatment. Her need to consult books made the author uneasy. It made her seem less competent than a doctor who could diagnose the condition and prescribe treatment without having to look it up. Later research he conducted confirmed that most people shared his feelings, and felt the doctor who had to look things up was less competent. But why was this?

The authors hypothesize that we tend to judge a person's competence by their confidence. A doctor who confidently diagnoses a condition seems more competent than one who is less certain and needs to consult a reference. This is likely because confidence is usually the result of experience. A doctor who had seen a particular condition many times will confidently diagnose and treat it. Where confidence is a result of experience, which it typically is, it really is a valid measure of competence. But what about when the confidence displayed is not warranted?

Would it have been better for the author's doctor to confidently assert she knew the cause of his rash when she wasn't certain? Obviously not. By checking her references, she confirmed her diagnosis and was able to find the proper treatment. Checking was clearly better than confidently giving an unjustified diagnosis. Yet the author would have trusted her diagnosis more if she had done just that.
I think the cognitive bias of confidence is part of the explanation for why many people perceive religious doctrine to be more trustworthy  than scientific conclusions. Religious doctrine confidently asserts its truths. Science, on the other hand, can give only tentative conclusions, contingent on the evidence. Religion steadfastly maintains confidence in its doctrines, while scientific theories are often refined and occasionally completely overthrown as more information becomes available. Who is more believable, the rav who confidently asserts that evolution is nonsense, or the scientist who says that the evidence leads him to conclude that different species evolved, though he can't be sure about the mechanism for this detail and who used to think that dinosaurs were scaly, but now says they had feathers!?

Unfortunately, the confidence with which religious doctrines are asserted  is not the result of expertise, but of faith. They are accepted primarily because the religion requires acceptance  of those doctrines and vilifies disagreement with them as heresy. No one has expertise in the unity of God, or the resurrection of the dead. Yet these and many other religious precepts are confidently asserted, and that confidence creates an unwarranted sense of their reliability.

[1] Chabris, C. F., & Simons, D. J. (2010). The invisible gorilla: And other ways our intuitions deceive us. New York: Crown.