The scientific consensus is embryos should not be considered the same as fully developed people. Two-thirds of embryos fail to develop. At that point in human development, the embryo is a collection of a few cells. In a technical sense, all of the genetic material is present but there is nothing intrinsically human or valuable there. It's just a bunch of cells.
But Sandel finds further flaws with the equal moral status view. "The fact that all persons were once blastocysts does not prove that all blastocysts are persons. This is faulty reasoning. The fact that every oak tree was once an acorn does not prove that every acorn is an oak tree" or that we should regard the loss of an acorn eaten by a squirrel as equivalent to the loss of an oak tree felled by a windstorm.
The potential for life is not enough to qualify something for the same rights as a fully developed human being. Here's another way to look at it.
Developmental biologist Douglas Melton, for his part, does not believe the cells of a blastocyst, which has neither nerves, heart, lungs, brain, feeling, nor any sensibility at all, are a human being. "You can't put a five-year-old in a freezer and then take it out" as you can a blastocyst, he says.
Pro-life advocates say what's important is the embryo's potential for life. There is no single moment when an embryo suddenly develops into a human. If something has the potential to become a human, then it should have a right to life.
George holds what is known among moral philosophers as the "equal moral status" view of the human embryo: "The principle to which I subscribe is one that says that all human beings are equal, and ought not to be harmed or considered to be less than human on the basis of age or size or stage of development or condition of dependency." Fertilization "produces a new and complete, though immature, organism" that possesses "the epigenetic primordia for self-directed growth into adulthood with its determinateness and identity fully intact." Although not all fertilization events lead to an adult, we were all once embryos in the blastocyst stage of development, he points out. We possessed all of the genetic material needed to inform and organize our growth.
Human equality means all humans are equal. If human worth is intrinsic, them embryos intrinsically have a right to life.
Humans deserve full respect by virtue of the kind of entity they are, George maintains, not by virtue of acquired characteristics or abilities, which we all hold in varying degrees even once fully grown. Development is a continuous process: there is no special moment when human life suddenly becomes worthy of respect and human rights. That worth is intrinsic, he argues. Embryos, therefore, should not be used as means to an end, even good ends such as cures for diseases or to save another human life.