Phased & Substance Sortals: Existence and continued existence

When we discuss and argue about moral possibility of toleration or acceptance of abortion, we should learn the divergent opinions on concept of identity, existence and continued existence in order to hopefully grasp some clearer understanding of a life, person or person and personhood, and a thing, and whether a life is a thing or beyond a thing.

To gain more fruitful discussion, we should learn logician's concept of sortals:
(a) phased sortals,
(b) substance sortals

and try to understand statements like:
(a) A phased sortal designates a kind to which an individual may belong through only part of its history.
(b) A substance sortal designates a kind to which an individual necessarily belongs throughout its entire existence.

and
(i) If "x" is a substance sortal, there are criteria for being an "x" that any "x" must satisfy as long as it exists.

(ii) The criteria given by the substance sortal appear to state only a NECESSARY condition for the continued existence of an individual of the kind "x". It is not always SUFFICIENT for the continued existence of an individual "x" that, beginning with that individual, one can trace the continuous presence through space and time of an "x".

The above relates to the problem we come across when we face diffculties in agreeing on personal identity over time and ask what is necessarily involved in our continued existence. For one could cease to be a person without ceasing to exist, just as a child  may cease to be a child without ceasing to exist, [for example].

[The above are extracted out from J. McMahan's The Ethics of Killing: Problems at The Margins of Life, Oxford: OUP, page 6 & 7 (2002)]

Concerning the physical criterion of personal identity, at least 3 important questions have been asked by D. Parfit in his book: Resons and Persons, Oxford: Clarendon (1987) , page 202:-
(a) What is the nature of a person?
(b) What makes a person at 2 different times one and the same person? What is necessarily involved in the continued existence of each person over time?
(c) What is in fact involved in the continued existence of each person over time?

Please do not just limit oour thoughts on abortion when we read and re-read the above questions.

Please also think about whether there are contradictions, dilemma and paradoxes already "built-in" or concealed behind the questions that even Parfit, and later, McMahan, may have missed out in their discussions.

The above questions, no matter what, do open up our visions and at the same time, define more clearly some crucial points and scope that we should not ignore when we try to justify the pro-choice or pro-life positions on the topic about abortion.

The above questions help us check whether we may come into agreement on what we mean by "organism", "human", "human organism", and "human being".

Later, I may try to provide some more details on sortals and recognition as part of my studies about "stages, sortals and possible world" as written by A. Brennan