It is an intentional tactic on the part of some who push for the instrumental use of nascent human life to make the sophistical argument that human embryos are not really organisms until they implant in a uterus. Ironically, these advocates make this bogus claim in the name of boosting science. But this is anti-science because it is utterly inaccurate from a biological perspective. But the point is to tie opponents down with endless and circular debates about what constitutes a living human organism so that the real discussion about whether and when it is appropriate to use human life instrumentally can be avoided.
I am really tired of dealing with this over and over again, but will make this one last foray into the issue: Let’s look at the caterpillar that becomes a butterfly. It is the same animal when it is a worm-like creature with many legs that it is later after it has metamorphosed into a beautiful butterfly that can fly. The butterfly isn’t a different individual member of that species. It is the same member of that species–it is just in a different stage of development with different capacities. When it is a caterpillar, it can eat leaves but it has no wings. Still, it has the developmental potential to fly. It isn’t any less a member of its species of butterfly when it is a caterpillar than after it leaves the cocoon.
Similarly, when it comes to being an individual member of the human species, an embryo, is a fetus, is a neonate, is a pre-pubescent, is a pubescent, is an old man like me. During my nearly sixty years, I have never ceased being the same individual member of the species Homo sapiens I was when my life began upon completion of the fertilization process. My voice is deeper than it was when I was five. I had more hair and it was dark brown when I was 20, I had more neural cells when I was 30. My genes were expressing differently when I was seven than they are today. But I did not become a different organism. I have, since I was at the one-cell stage, been the same organism. Nor did my implantation in my mother’s womb make me a different organism than in the week or so when I was in her fallopian tube.
That is basic science that is beyond dispute from a purely scientific perspective.