A number of people have attempted to clarify what actually constitutes a “person”. Firstly, it needs to be capable of rational thought. The ability to solve problems using the power of reason distinguishes humans from animals or from human tissue. Whilst a newborn baby is not a rational individual, it does have the potential to develop rational thought. This situation becomes unclear and difficulty arises with the status of a severely handicapped adult.
Secondly, does the “person” have a form of consciousness that enables them to feel pain or pleasure? This principle is by all means wide enough to include newborn babies, well-developed fetuses and severely handicapped adults. However, the problem from this is that it would include animals. Self-awareness must be taken into account. This means that the individual knows they belong to society, is aware of past events and has a sense of their own identity, three crucial aspects. It is not believed that animals have this sort of awareness, but then again neither do babies or some severely handicapped adults. Related to this point, it would require being able to survive independently as a human. This definition would clarify the status of a foetus or human tissue but is open to debate when a person is dependent on kidney dialysis or any other medical support system/process for their life. Furthermore, it has also been identified that a baby can only survive with adult support. So, due to the above points related to personhood, the argument of defining what is a human person is extremely open and strife debate occurs as a result. However, what is also important to take into consideration is when the foetus is a person. Firstly, conception is an obvious example. This case is supported by the fact that from the moment of fertilization, genetically the egg contains everything that will make it a unique individual. Also, it could be at some stage during development. Various stages have been suggested, such as from the moment a mother can feel foetal movement, or the stage at which the foetus can feel pain, or the moment when the foetus can survive outside the womb, or the moment when the soul enters the foetus. It may even simply be at birth, when it can lead a life that is independent of its mother.
If the foetus is always a person, then it would be necessary to repeal all the existing abortion control laws and ban abortion except in self-defence, or justifications about killing must be evident, including having a disability and causing some other person mental or physical distress. To be consistent, we would then need to permit killing other types of people, such as adults, for the same reasons.
The other possibility is that the foetus is never a person until it fully emerges from the birth canal. That is to say, personhood is defined by the foetus/baby's location in three-dimensional space. This would make it reasonable to kill it at any time while it was still inside the womb, but it would also mean having a definition of personhood which was not intrinsic. However, it's clear that this is also not the stance of UK law. If it were, abortion laws would not exist.
It also may be the case that the foetus is a person some of the time. If we forget about if the foetus is always or never a person, then the remaining logical option must be the position of UK law. This would mean that abortion law is an attempt to define under what circumstances a foetus is a person, thereby preventing it being killed when it is, and allowing it when it isn't.