Aquinas developed the Natural law Theory, with which he proposed five ‘telos’ that he believed were our duty to follow. His 5 primary precepts- ‘Worship God Ordered society, Reproduction, Learning and Defend the innocent’ are deontological. However, whilst being deontological, Natural Law does have some flexibility with the more teleological, secondary precepts.
The doctrine of Double effect refers to situations where there is an intended outcome and another significant but unintentional outcome. According to Natural Law, it is our intentions that are important, not the consequences of our actions. Double effect would not allow you to perform an action where an unintended outcome had devastating effects. The unintended effect has to be proportionate. In this way, Natural Law becomes like Utilitarianism. This can be applied to sexual ethics for example, in the case of an ectopic pregnancy. This is where the foetus attaches itself to the mother’s fallopian tube. This is potentially life threatening to the mother, and in turn, the child itself. Natural law views Abortion is an evil act, and therefore not an option. However, removing a fallopian tube, with the secondary effect that the pregnancy ends, is not an evil act. When carrying out an act with two effects, you ask whether the second effect is proportionate. In this case it is. In other words, it is unethical to abort an ectopic pregnancy (which would leave the woman able to have another child), but ethical to remove an ovary (which, in cases where a woman has one working ovary, would leave her unable to have future children).
With this in mind, it could be argued that this flexibility makes Natural Law a very reliable approach regarding sexual ethics, as it isn’t entirely an absolutist theory. Nevertheless, the problem lies within the precepts, as if you do not view them as our soul