What is the Torah position with regard to the preservation of life when facing certain death? Are we duty bound to accept or continue chemotherapy, for example, when life becomes full of illness and pain? To what extent must we protect and preserve our own life, and at what personal cost in terms of pain and suffering?
This is an excellent and very involved question. Medical Halacha (Law) is a very complicated topic and has tremendous variations from situation to situation. No two situations are the same, and when a medical question arises, it is very important to consult with a Rabbi who is an expert in these areas.
That being said, the general rule is to preserve life at all costs – even in the face of suffering and “certain death.” The reason for this is two-fold: Firstly, who is to say that they will not discover some new medical advance tomorrow that will help in today’s situation. Additionally, although suffering is not pleasurable, it is purposeful. Therefore, although we will do anything possible to alleviate the pain of another, this is usually not enough of a reason to end a person’s life.