Final answer:
The acquisition of a rational soul by a fetus is a complex issue that intersects with philosophy, theology, and moral reasoning, and is not solely a matter of biological development. Different historical, religious, and metaphysical perspectives have informed when the soul is believed to enter the fetus, and modern debates often focus on the concept of personhood and the moral rights of a fetus.
Step-by-step explanation:
The question of when a fetus acquires a rational soul is not purely a scientific matter but intersects with philosophy, theology, and moral reasoning. Historically, theories of ensoulment have been informed by religious and metaphysical perspectives, and the debate includes the practical implications these views hold for the moral status of the fetus.
In terms of fetal development, by the fetal stage, which begins at approximately nine weeks after fertilization, the organism has developed to a point where it is recognizable as a human, with all major organs present, though not yet fully functional. From the Aristotelian and medieval Christian views, such as those by Thomas Aquinas, ensoulment was believed to occur at a specified time after conception. This was later challenged by Pope Pius IX, who stated the soul is present from conception.
Modern arguments often revolve around the concept of personhood and whether potentiality, such as innate human potential, grants moral status or rights. Critics like Warren contend that a fetus lacks the criteria for personhood and hence does not enjoy moral rights.
The discussion includes diverse perspectives including those of major monotheistic religions, and the issue of ensoulment remains pivotal in considerations of abortion and the moral treatment of human fetuses.