The answer is: we can’t, or rather, we shouldn’t. By using natural law as a criterion for positive law, the realm of religion is infused into legislation. Each religion has its own set of moral standards and values and although most overlap and have similar tenants, on what standards if not religious ones would a secular government be judging morality.
This idea of natural law being a basis for judging positive law conflicts when considering the debate over abortion. In 1973 the landmark decision in Roe v Wade found that the mother had a right to abortion until viability. Since then, Congress has tried numerous times to enact laws to ban abortion that could cause doctors to face penalties of prison and civil lawsuits. None have been successful and now the topic varies state-by-state. Personhood USA “is a movement working to respect the God-given right to life by recognizing all human beings as persons who are “created in the image of God” from the beginning of their biological development, without exceptions” (personhoodusa.com). The basis for the anti-abortion argument is purely driven by religion. If natural law is used to judge positive law then any law enacted aims to serve the common good. However, since this law would legislate based on religion and everyone does not believe in the same religion it would not serve the common good. Although some people are pro-life and have certain beliefs on when life begins, is it for the common good that every baby is born?
When considering whether natural law can serve as a basis to judge positive law (or lack thereof in this case) consider these statistics:
- 21% of abortions are because the parents cannot afford a baby
- Having a baby born into a family that cannot afford it can arguably hurt the common good by placing more people on welfare
- 10% of abortions are because it will interrupt education or a job
- Having a baby while one is still in school disables the parents from gaining an education which would benefit the common good
This is an extreme example where natural law should not be the basis for the formation of a positive law. In a secular country where freedom of religion is a basic right, morality is too subjective from person to person and from religion to religion. Those with opposing or differing morals can challenge any law that is upheld by morality or when natural law is used as criterion for positive law, which would make for messy legislation and legal system. In a perfect world, positive laws would be morally upright and made to serve the common good, but humans are imperfect and everyone has different conceptions of what is morally right and wrong and how to serve the common good.