To begin, from what I understand, stem cells are basically blank. Heart cells, nerve cells, liver cells, bone cells, skin cells or any thing that provides a function needs to be told what it is, and how to work. The DNA / nucleus is like a computer chip. Without software, or in the case of a cell RNA, is needed before it can do something or produce any useful work. They do not yet have a purpose. In the case of an embryo, the only job in the early stages is for it to simply make copies of itself. Once there is a large enough group of them, it can be time to start giving those cells any of a wide range of jobs, like become part of a heart, lungs, nerves, or whatever is needed. There cells work together dedicating their life to whatever job they are assigned. They live out a lifecycle like people, but much much shorter. A thing about heart cells though, once they are programmed, they can either do their job as a part of the heart, or divide to make new replacement heart cells. Because they are programmed with a particular code, what ever the job of the parent was, so will be the job of the children. Heart cells can not become lung cells, for example because they were not designed that way.
So here is where stem cells are totally unique. They have no job yet. They have not been told what their task will be that it will provide or that its children will provide in all future generations. Remember that once programmed, they can never be reprogrammed. They dedicate their life to their work.
Amazing things have been done with transplants and graphs. Hearts can be taken from one person that can no longer serve another's life, but can be given to another where both can continue to live. burn victims can have damaged skin removed, and other skin can take its place, and those cells continue to do their job.
If we define our life by who we are uniquely and our role in society by what we do in all aspects, it could be said that stem cells are not yet alive. They are the tools that are used to become life.
There are limits on what scientists can do with transplants. We do not worry that because, say, a liver played the role of cleaning a persons body that somehow the persons soul is going to be damaged by playing that same role in another body.
scientists want to extend that to a smaller level. While stem cells are the building blocks for life, they have not been told what to do yet. In nature, at some point in natural development, those cells will be given a job, and what scientists want to do is guide those cells to do what they do naturally. Instead of becoming an entire new life with enough time and programming, doctors can put those cells into a person with a spinal cord injury, and being near those cells, the stem cells will see "This person needs a section of their spinal cord". even if microscopic, the cells can communicate with each other, and the stem cells will know their purpose in life, and take on the role of being a part of that spinal cord.
Being totally unprogrammed, and being so small, stem cells can take on the tiniest of tasks as they were meant to, and with no prior knowledge, completely integrate itself into the hosts system without chance for rejection of complications due to conflicting programming.
Programmed cells can not be reprogrammed. If the stems cells were a life, or meant to be a baby, the kinds of issues that in adults that could be resolved though stem cell therapy would not work. If the cells were meant to become a new life, they would. Instead, in an adult with a disease or injury, the stem cells will want to help repair the damage and become a part of another life as nature intended.
This miracle of life that we have slowly come to understand is not simple. It isn't just a shot, or a bandaid any more than heart transplants, or skin graphs were just easy things. There is more that needs to be known, and this is why for real progress of medical science, we need to study these things, and understand how this works to provide the environment necessary for these stem cells to do what they do naturally.
In whatever respect stem cells could be considered to be alive, it is not like growing children to harvest hearts where a child is killed and their bodies discarded. Such a wretched disregard for life is and should be deplorable. In the case of stem cells, all the cells can be used in a manner already intended by nature. Even if a group of cells were divided, these cells can still do any job necessary. As we already see in nature, this can happen under normal circumstances to create identical twins. In whatever way we may see identical twins the same, they are not one life, they are individuals as complete as any other person. As we have recently discovered, the opposite can be true. In the case of fraternal twins, two eggs each separately fertilized can be joined together. If this is very late in development when these cells have start to become a complete person, there can be upsetting results, Siamese twins. In Siamese twins, two to be children mostly developed can combine at a stage to complete one part of the body together that is shared. Sometimes this may just be skin, and the twins are easily separated, and being disconnected, a normal healing process will begin to complete the missing parts individually; this is one of the many roles of programmed skin cells. Sadly in earlier development, children may join together to make one spinal column, at which point the pair would either live out life with a very difficult disability, one twin may be killed to save the life of the other, but more often than not, this will result in a still-birth, as the machine that is our bodies will either recognize the result and self terminate, or simply fail on its own.
Another type of twin though has been recently discovered, a Chimera. Like a Siamese twin, but where the combination is almost completely stem cells. In this case, the child will develop completely normal and healthy, just with 2 (or possibly more) sets of DNA. Because they were combined so early, there are no complications because there is so sense of identity by one to reject the other. Perfect symbioses.
but in the way stem cells work, some group may become bone marrow, while the others of the different DNA may become skin. This has brought a whole new complication to DNA testing, because while DNA testing of one tissue type may measure one way, a blood sample from the same person can come back as a mismatch. Checking the same person from different tissue samples was never considered, and in the case of, say, DNA evidence for a homicide or rape, a Chimera has a solid defense in our current system.
So what do we say of these different people, and types of twins; one where we see what we call "life" divided, and others where two lives may have been combined. What does it all mean? It means there is a lot about life and particularly stem cells that we do not understand in their role.
We do separate Siamese twins in hopes of providing a quality of life to individuals, and Chimeras can be totally normal and healthy. We do not accuse identical twins of only having half of a life, nor should we. It is an opportunity to understand what is revealing itself as an amazing process that is life.
Cells without a purpose in life can become any number of things as we have seen in nature in nearly infinite ways. Stem Cell research can take cells that want to provide for a life in a new way to improve the quality of life for many individuals that where either their stem cells or DNA might not have gotten things right the first time. Doctors will hopefully one day to correct such mistakes with Stem Cells doing just what nature intended.
To try and stop stem cell research because one can not open their mind to the multifaceted and nearly incomprehensible miracle of life beyond what we currently understand is brutally unethical. Please allow thinking to guide our progress, not ignorance.