Throughout Christian history, natural law has been one of the most influential moral and philosophical theories, providing a link between God and human morality. It's a theory that dates back to the works of Aristotle, who argued that everything in life has a purpose or objective, a concept developed by St. Thomas Aquinas in the 13th century. However between this transition, the Roman philosopher Cicero stated this; "true law is right reason in accordance with nature. It is universally applied and is immutable and eternal,"1 which implies that natural law should apply to all modern ethical dilemmas. This essay will explore the credibility of natural law in a modern context by examining two modern ethical issues. A credible theory is one that is found to be convincing and believable and this essay will first examine how the Catholic Church and natural law have responded to modern fertility practices, exploring in vitro fertilization (IVF) practices and male sterility testing. Secondly it will explore the issue of modern medical abortions. Concluding how much natural law can offer a credible response depends on the individual and social groups. Throughout the history of natural law, all scholars have agreed that its primary principle is that everything in this world has a purpose, often agreeing that this purpose was designed by God. The natural law we think of today is predominantly the version presented by Aquinas, who “considered that natural law was the moral code towards which human beings are naturally inclined. God reveals specific commands, but these do not go against natural law but rather go beyond and develop it.”2 For Aquania's theory of natural law, one of its key principles...... half of the document .... ..it is a similar response to the personal one. However, there are also groups who will not find natural law credible because they would find it difficult to believe that the Church has the right to tell women what to do with their bodies. In my personal opinion and experience, I would say that the Church and natural law are losing credibility. They still have a huge influence on society and decision-making processes around the world, but when it comes to ethical issues, humanitarian approaches are starting to prevail. However, I think it is unfair to consider natural law useless because it still has a strong basis in the world. Many humanitarian laws derive from principles such as natural law. Ethical issues are also inherently complex, each with its own pros and cons, so natural law cannot be said to be entirely useless or entirely relevant..