The Torah states: I am the L-rd that heals you! (Exodus 15:26) This verse implies that G-d does not need man to cure the afflictions that He creates. If so, by what virtue does man attempt to short circuit His will and attempt his own meager cures? Does man have any right to heal at all, and if he does, are there any limitations on how it may be accomplished. Is every action done in the name of therapy justified, solely because a physician performs it? Because Judaism recognizes the enormity of these questions, it requires direct permission from G-d to permit the practice of medicine and carefully circumscribes the limits of medical practice. Fortunately, the duty to save one's fellow man is well grounded in the Torah and the restrictions are discussed at length in our codes of Jewish law.
The Talmud derives the obligation to rescue one's endangered fellow from the verse Do not stand idly by the blood of your neighbor (Leviticus 19:16). This verse requires one to prevent accidents or injuries, it does not imply any duty to heal . The obligation to heal is traditionally derived from Exodus 21:18-19: And if two men fight, and one hits the other with a stone or his fist, and [the victim] does not die. . . [the aggressor] shall cause [the victim] to be thoroughly healed (i.e. pay the physician's bill). It naturally follows that if one must pay the doctor's bill, the physician must be allowed to treat the patient.
Alternatively, Maimonides derives the obligation to heal from the verse and you shall return it [a lost object] to him(Deuteronomy 22:2). While other commentators interpret this verse to command us to return a person's lost body as well as his lost property (i.e. aid one's friend in times of danger), Maimonides goes further and derives the obligation of physicians to treat patients from this verse. Further, he states that this verse represents a Biblical commandment to every person, each according to his ability, to restore the health of his fellow man. So not only may we not stand idly by as our neighbor is endangered, but we must aggressively attempt to return his health to him, including utilizing medical treatments.
But with the sacred privilege of healing comes inherent limitations. For example, the thought of a physician assisting a patient to commit suicide is anathema to a Jewish view of medicine. Physicians (and for that matter, anyone else with medical knowledge such as nurses, EMT's, or lifeguards) are granted a mandate to heal However, it is unequivocally clear from halacha that permission is granted to a physician to treat a patient only when he can offer that patient therapy that can be reasonably expected to be efficacious (this, at times, may include even experimental treatments which could be helpful).
When a physician cannot offer effective therapy, cannot alleviate pain, and cannot cure the patient, he ceases to function as a physician. In such a case, he has no more of a license than anyone else to cause harm to another person. Physician-assisted suicide is just plain wrong because it undermines the mandate which the Torah grants to physicians to be G-d's partners in the treatment of the sick.
The Jewish view of medicine is possibly best expressed by the Shulchan Aruch (Code of Jewish Law) when it explains both the great opportunity and the awesome responsibility that is granted to physicians:
The Torah gives permission to the physician to heal; moreover, this is a religious obligation and it is included in the obligation of saving a life. If he withholds his services, he is considered a shedder of blood. . . . However, one may not engage in healing unless he is an expert and there is none better qualified than him present, because if this is not the case, he is considered a shedder of blood. (Yoreh Deah 336: 1)
Sources: Maimonides: Health in the Jewish World, Vol. 2, No. 2 (Summer 1996), The Institute for Jewish Medical Ethics. I would be happy to hear from anyone with questions on this topic or who is interested in further information on other Jewish medical ethics topics. My e-mail address is firstname.lastname@example.org, web. www.daneisenberg.com