Genetic Engineering in Halacha – Part 3 by Ariel Caplan


Last week, we demonstrated that although a prohibition of Kilayim – mixing plant species together or mating animal species together – exists, genetic engineering does not pose any Halachic problem when done with animals, and there is likely little issue in plants as well. However, beyond the Halachic issues, we must address the ethical question of interfering with nature on such a fundamental level. Does the Torah consider it appropriate to tamper with natural phenomena and create new species? Is this an inappropriate flexing of the muscles of scientific progress?

Mastering Nature – License and Imperative

At the end of the first Perek of BeReishit, we are told of the creation of humans. Hashem’s first action in relation to Man is to give a blessing: “Be fruitful and multiply and fill the earth, and conquer it, and rule over the fish of the sea and the birds of the sky, and all the animals that swarm the earth” (BeReishit 1:28). Commenting on the word “VeChivshuha” (“and conquer it”), Ramban writes, “[God] gave [humanity] power and authorization to do as they want with animals and vermin and creatures that crawl in the dust, and to build and uproot the planted, and to mine copper from the mountains, and the like.” Seforno (ad loc.) relates “conquer it, and rule...” specifically to mastery over animals. He states that with these words, God commanded us, “Hold back the animals so they should not enter your domain, and reign over them, and rule with traps…to bring them into your service.” It seems from these explanations that we may do as we please with natural resources, although there is no specific injunction to do so.

However, in essays such as The Lonely Man of Faith, Rav Yosef Dov Soloveitchik develops a more enthusiastic approach toward man’s responsibility to build and develop the world. He describes man as a dual creature, whose nature and fulfillment emerge through engagement with both physical and spiritual worlds.

In his article on genetic engineering, Rav J. David Bleich notes two more sources in support of building the natural world. The first is the story of Rabi Akiva and Turnus Rufus (presented in Midrash Tanchuma to Parashat Tazria), where Rabi Akiva notes the value in developing wheat into cake. The second is the comments of Tiferet Yonatan and Beit HaLevi on BeReishit 17:11; both develop the idea that God created the world in an imperfect state, and man must bring the elements to completion.

Whether or not one accepts the more encouraging approaches, there is certainly permission to develop the world and use all its bounty for the good of humanity. Genetic engineering has already demonstrated its potential for use as a tool in treatment of disease, improvement of the durability and nutritional value of crop plants, and furthering of scientific understanding. It has allowed the creation of plants, animals, and bacteria which serve as organic medicine factories. There is no question that it greatly benefits humanity. Assuming that genetic engineering is Halachically and ethically permissible, we should encourage its pursuit. However, we must consider the possibility that tampering with the fundamental elements of organic life oversteps our boundaries.

As in Halacha, the ethical debate surrounds the prohibitions of Kilayim. The interbreeding of animals or plants produces offspring which are fundamentally different from their parents, prompting those commentators who address moral implications of Mitzvot to address issues of tampering with nature in the context of Kilayim.

Rashi’s Approach

The Pasuk in VaYikra that forbids various forms of Kilayim states, “Keep my Chukim [laws]; do not breed your animal as Kilayim, do not plant your field as Kilayim, and a Kilayim garment of Shaatnez shall not be upon you.” Addressing the phrase “Keep my Chukim,” Rashi states, “These Chukim are decrees of the King [i.e. God], for there is no reason for the matter.” He seems to believe that Kilayim prohibitions are simple regulations created by God with no specific motivation other than to give us commandments to fulfill; if so, there is no moral reason to extend the prohibitions to anything beyond their exact definitions.

Rambam’s Approach

In Moreh HaNevuchim 3:37, Rambam discusses various prohibitions which, he feels, exist to separate us from idolatrous practices followed at the time the Torah was given. (His thesis is rooted in research into idolatrous practices that existed at the time, as chronicled in ancient works to which he had access.) Among these prohibitions are those of Kilayim. If this is true, there is no reason to extend Kilayim beyond those actions which are directly prohibited, as the ethical mandate is not to avoid tampering with nature but rather to refrain from specific idolatrous actions.

Ramban’s Approach

Rabbeinu Bachya, Rashbam, Ibn Ezra, Ramban, Seforno, and Sefer HaChinuch all offer the same explanation for the Kilayim prohibitions (albeit with some nuanced distinctions), namely that mixing plants or animals constitutes inappropriately tampering with God’s creation. While all of these commentators are significant, this interpretation is generally credited to Ramban, as he gives the most complete explanation of what makes Kilayim morally wrong.

Ramban writes that initially God created all necessary species in the world, and He gave them reproductive capabilities to allow their continuity as long as the world exists. If we crossbreed animals, argues Ramban, we imply that God did not create everything that the world needs and that it is our prerogative to add new creations. Regarding plants, Ramban writes that planting them together causes them to derive nutrition from each other and change form, which presents the same theological problem.

Ramban adds two supplementary reasons to this rationale. One is that the products of Kilayim are sterile, in both plant and animal worlds. The other is that the powers in the upper spheres which relate to each species on Earth will be inappropriately mixed.

Reconciling Ramban

Ramban’s comments regarding Kilayim seem to constitute a radical departure from that which he stated in BeReishit regarding our permission to conquer nature. How can we reconcile the two statements?

Perhaps Ramban in BeReishit never meant to deal with creating anything new; rather, he referred to the use, modification, and improvement of preexisting entities. Ramban might feel that we may engage in creative activity only as long as we respect the distinctions between entities that already exist. We may use horses and donkeys for manual labor, but we may never unite them to make a mule. (Dr. Abraham S. Abraham suggests this approach to Ramban to defend him from Gur Aryeh; see Nishmat Avraham, Hebrew edition, 2007 printing, v.4 p.184.)

If this idea is correct, Ramban would not look favorably upon genetic engineering, which does not respect natural boundaries and creates new plants and animals (although only minor modifications are scientifically achievable at this point in time).

A Limited Prohibition

It is interesting to note that despite the strong comments of Ramban, Halachic authorities who addressed Kilayim, specifically Rav Shlomo Zalman Auerbach and Chazon Ish, never dealt with the ethical ramifications. The miniscule extent of the prohibition of Kilayim of animals, the limitation of Kilayim of plants to Eretz Yisrael (although grafting is prohibited anywhere), and the exception of bitter plants also should engender some surprise. Perhaps in the specific context of Kilayim, the parameters of Halacha are all that is ethically proscribed. Why would this be?

We might answer that Kilayim is not really meant to prevent our intervention in Creation; rather, it is meant to instill within us a sense of respect and appreciation for the universe and the diversity of life that God created. This goal is achieved by abstaining from the Halachically prohibited actions alone, and it is not necessary to extend the prohibitions of Kilayim to any actions outside of these parameters.

If we understand Kilayim in this way, perhaps genetic engineering should be not only condoned, but even encouraged. As scientific research progresses, we are able to appreciate the Creation more and more. By striking the correct balance between avoiding Halachically prohibited actions and pursuing Halachically permitted investigations of nature, we can fulfill this interpretation of the “spirit of the law” of Kilayim to the greatest extent possible.

This approach is not compatible with Ramban, who seems to oppose all interference with nature, and would likely disapprove of even Halachically permissible actions. However, it could be used to narrow Ramban’s camp; most of those agreeing with Ramban state their position less emphatically, and perhaps their sense of a value for order in the universe would be satisfied by the Halachic boundaries alone.

Alternatively, we might take a somewhat less bold stance and accept the kernel of Ramban’s idea, without taking it to his extreme. Perhaps the Kilayim prohibitions indicate to us that toying around with the fundamentals of natural phenomena is indeed a dangerous game, one that must be approached with caution, and with respect for the unimaginably complex biosphere that has been granted to us. (In personal conversation, Rav Michael Rosensweig indicated that this concept would likely be accepted by all, regardless of their comments specifically regarding Kilayim.) We will return to this point later.

Do Reasons Matter?

Our entire discussion to this point has assumed that the reason for the Mitzvah can establish an imperative to perform or refrain from an activity. However, great Torah figures of the last century have limited this principle, to varying degrees.

In both Igrot Moshe (Cheilek Kodashim VeTaharot 15) and Dibrot Moshe (addendum to Ketubot), Rav Moshe Feinstein writes strongly against deriving Halachic conclusions, whether stringent or lenient, from the reasons for Mitzvot. In the former piece, Rav Moshe draws a fine line between ethical rationales and actual Halacha. Where Halacha is concerned, no conclusions whatsoever may be drawn from the reasons for Mitzvot. Ethical principles may be derived from Mitzvot, but only where they do not contradict the Halacha. Additionally, we might add, ethical principles are not set in stone as is Halacha, and they must be balanced with other ethical principles in real-world application.

In Halakhic Mind and Worship of the Heart, Rav Soloveitchik develops the idea that our ethical principles should be grounded in the Halacha rather than in Aggadic material. This idea emerges from two elements of Rav Soloveitchik’s philosophy. The first is the centrality of Halacha in Jewish thought. The second element is the practical consideration that it is much easier to misunderstand or distort an Aggadic comment to yield a desired philosophical outcome.

Based on the positions of these two towering giants, we may well understand the issues noted in the previous section. The comments of Ramban and others notwithstanding, we should likely build our perception of the ethical issues out of the Halachic principles, which – as noted – severely limit the Kilayim restrictions. Although Rav Moshe certainly leaves room for ethical principles, the ideas of building the world and benefiting humanity likely overshadow an ethical imperative to avoid tampering with nature. Considering that two major Halachic authorities of Eretz Yisrael of the previous century – the Chazon Ish and Rav Shlomo Zalman Auerbach – did not mention Hashkafic implications of Kilayim, and that two great American Halachic decisors – Rav Moshe Feinstein and Rav Soloveitchik – minimize the implications of Aggadic explanations of Mitzvot, it would seem that the combined trend of recent Torah authorities should limit the ethical restrictions of Kilayim and favor pursuit of genetic engineering.

The Responsibility to be Responsible

Genetic engineering is an exciting field, but it is also potentially hazardous. While applications in the laboratory setting are certainly harmless, mass production of genetically engineered organisms may carry along unintended side effects. Environmental effects of mass-produced genetically engineered plants and animals are potentially disastrous (though less so than some media sources would claim). Particularly of interest are unexpected toxic effects for the consumer of genetically engineered food, resulting from the complex network of interactions between genes and their products. Therefore, it is critical that products of genetic engineering be subjected to rigorous independent testing before release to the market. Irresponsible “advances” may do more harm than good, but responsible pursuit of this technology has tremendous potential to benefit humanity.


We have examined the comments of Rashi and Rambam to Kilayim, which imply no particular problem with genetic engineering. We have also noted that a large group of commentators, including Ramban, see Kilayim as a warning against tampering with nature. However, we have also noted several approaches that may mitigate the implications of Ramban’s camp. On the whole, it seems that a Torah approach to genetic engineering would be one of cautious optimism, balancing a sense of restraint and reluctance to interfere with Creation with the mandate to develop and improve the world. Genetic engineering in research or medicinal applications is less morally problematic, while mass distribution of genetically engineered consumer products must be approached carefully and responsibly.

Great Opportunities: Ten Conversations with Rav Soloveitchik by Rabbi Chaim Jachter

Genetic Engineering in Halacha – Part 2 by Ariel Caplan