The Rational/Ethical Assumption
We must assume that all children that we create would choose (if they had the choice) to be created free from known genetic diseases and into a world that sought to provide them with optimal lifelong individual happiness. This assumption can only be validated by asking ourselves what kind of world or genetic design we would want for ourselves and those we care about. Would we want to take on a known genetic disease or strong predisposition for disease involuntarily so that humanity can have greater genetic diversity? Do we want a society that is not designed with the lifelong individual happiness of ourselves and others in mind?
{If it is freedom of choice and diversity that we truly value - why not create children free from known bad genes and unreasonable predisposition for disease and then give them the option to adopt genetic diseases or disease predispositions when they have 'informed consent' at an adult stage? I think it's highly unlikely that anyone would choose to take on a disease at that point.}
A primary objection to pre-implantation genetic diagnosis and subsequent screening for diseases is that many genetic predispositions are complicated and attempting to screen for them would be an attempt to establish a likelihood for disease given known genetic expression. It's true that many diseases are complex - recently Chinese researchers found an estimated 400 genes that are linked with a predisposition towards drug addiction. However, this understanding of the complexity of genetic functionality should not dis-tract us from the fact that there is a long list of known bad genes - which can be defined as a single genetic option that leads to a medical disease in every instance. Presently, the wikipedia entry for genetic disease hosts a long list of known genetic diseases which involve a single genetic change whether it be a point mutation, deletion, chromosomal aberration, or trinucleotide repeat disorder.
Regardless of this knowledge, most couples opt to use preimplantation diagnosis not for ensuring the lifelong individual happiness of their children by eliminating known bad genes - but for sex selection. Even worse some parents have intentionally created children with the hope of giving them a genetic disease such as Down's syndrome or congenital hearing loss. This underscores the need to develop an international ethical committee for identifying known bad genes and enforcing their removal from the gene pool.
We can't assume that parents will do everything in their power to ensure that children are born free from disease. Presently, much procreation is accidental and unwanted.
We certainly don't want to make choices about likelihoods for disease when we don't fully understand the etiology behind specific symptoms - yet already we have identified many genetic options which lead to a strong predisposition for disease. In determining what constitutes an unreasonable predisposition for disease we must consider first and foremost the lifelong individual happiness of the child to be. Knowingly creating children with strong pre-dispositions for disease in order to perform certain functions for society is unethical even if we plan to treat them down the road - for it is they who have to live a lifetime with their genes not us. Like global warming, creating children with bad genes will hurt us immeasurably in the long run in terms of the evolution of our species and the ability to create a better world for everyone - though it may be easier for some to brush aside the ethical difficulties through prohibition of screening.
The Addiction
Presently society is unsustainable without creating new beings regularly - we plan for it and depend on the young to perform vital duties. Without new beings our economy would collapse, our military would crumble, and we would have no one to take care of us when our bodies and minds begin to fail. We are forced to focus on quantity rather than quality when creating human beings.
The Cure is Good for Everyone
1.) Better genes - freedom from known genetic diseases and unreasonable predisposition towards disease means a better life for us all collectively and individually. Lower expenditures on health care and social services related to fixing known bad genes means more resources can be put into scientific research and development aimed at improving the human condition.
2.) Universality - an ethical directive which binds humanity into a cohesive network aimed at universally valid ends may help us to create a world free from wasteful nationalistic competition (countering the Darwinian drive for domination through economic and military superiority). Millions are wasted daily in the global pursuit of nationalistic military strength. With a unified world government a relatively small force to eliminate terrorism would be sufficient.
We must define the universal desires of human consciousness and let these desires form the basis for our legal rational authorities which underlie public policy. Our leviathan must be universally valid. Cultural programming which occurs in a given society is distinct from the inherent desires of consciousness that we have after birth (while still tabula rasa). Namely;
to seek freedom from involuntary suffering
to seek greater happiness
to continue this process through continued existence
3.) Longevity - the means to rectify the aging process (as distinct from the developmental process) means greater freedom from dependence on the creation of new human beings to do what we are unable to do as we become aged. Longevity research should become a primary function of society - as the purpose of society should be to increase the lifelong individual happiness of all of it's citizens equally.
4.) Self-Sufficiency - we create problems for future generations to solve in order to have greater convenience and relative competitive prowess in the short term. Self-sufficiency comes not only through societal engineering but also by changing human nature so that we are content and self-satisfied without having to one-up each other constantly. Biotechnology can create methods by which we not only train ourselves to have greater ethical capacities and self-satisfaction but also change the biological requirements of our existence.
5.) Mandatory screening - just like we can't trust big pharma to regulate itself - parents must be forced to comply with genetic screening practices. To allow otherwise is an extreme and dangerous form of libertarianism that undermines our values.
6.) Procreational licenses - accidental pregnancies are a significant problem. We must ensure that all prospective parents go through a process to ensure that they want the pregnancy, are reasonably able to perform the duty as parents, and are taking steps to ensure that they will be good parents.
Counterpoints to frequent objections
1. There is no reason to assume that eliminating known bad genes will hurt our evolution and much reason to believe that it will benefit our evolution. By eliminating known bad genes we make way for new and potentially useful diversity.
2. Parents are not able to assume responsibility for treating children born with genetic defects - they can't fix them after the fact nor bear the responsibility for living a lifetime with a genetic disease. Parents can not possibly cover the societal expenses of coping with genetic diseases - both in the short and long-term.
3. We have a good working medical definition for disease as determined by the scientific medical community - those who object to a medical definition of disease for Down's syndrome (within the context of preimplantation genetic diagnosis for screening) are creating children to make themselves happy - they are not thinking about the evolution of our species and the wider societal impact of genetic diseases. Just like we don't create cancer patients to keep existing cancer patients company - we shouldn't create Down's syndrome children to continue a community of adults with developmental disabilities.
-------
References, further reading, and a forum to debate these ideas can be found here;
http://www.abolitionist-society.com/forum/viewtopic.php?p=3719