HUMANITY
DEFINING
What is Life?
The question “What is life?” has long challenged scientists and philosophers, and no single definition has achieved universal agreement. In biology, life is typically identified not by a single defining trait but by a constellation of shared characteristics. Living organisms exhibit organized structure, growth and development, responsiveness to their environment, internal regulation (homeostasis), metabolism, and the capacity for adaptation and evolution. It is the combined presence of these features—rather than any one alone—that distinguishes living systems from nonliving matter. ( 1 )
In evolutionary biology and astrobiology, life is often understood as a process rather than a static category. A widely cited scientific formulation describes life as a “self-sustaining chemical system capable of Darwinian evolution.” ( 2 ) This approach emphasizes that living systems must both maintain themselves through internally regulated chemical activity and persist over time through heritable change. Participation in this ongoing process of biological continuity is widely regarded as a defining feature of life.
When applied to humans, these same biological principles fully and consistently apply. Human beings are living organisms characterized by cellular organization, metabolism, responsiveness, and self-directed growth. Human life is not defined by size, environment, degree of dependency, or stage of development, but by membership in the human species and participation in the continuous biological process characteristic of living organisms. Standard human embryology texts describe the beginning of this process as the point at which a new, genetically distinct human organism comes into existence and initiates its own coordinated development. The moment of fertilization. ( 3 )
What is Death?
In medicine and law, death is understood as the irreversible loss of the body’s capacity to function as an integrated organism. Rather than a single moment, death marks the point at which vital systems permanently cease to sustain life. Modern definitions emphasize irreversibility—meaning the lost functions cannot return spontaneously or through medical intervention. ( 4 )
In the United States and many other countries, death is formally defined by the Uniform Determination of Death Act (1981). ( 5 ) Under this standard, a person is considered dead when there is either irreversible cessation of circulatory and respiratory functions or irreversible cessation of all functions of the entire brain, including the brainstem, with determination made according to accepted medical standards. This framework reflects long-standing medical consensus and provides consistency across clinical, ethical, and legal contexts. ( 4 )
Traditionally, death was identified by the permanent stopping of the heart and breathing. Sustained loss of circulation deprives organs—especially the brain—of oxygen, leading to widespread and irreversible failure. Advances in critical care, however, have made it possible to artificially maintain circulation and ventilation even after catastrophic brain injury. In such cases, medicine recognizes death by neurologic criteria (brain death), defined as the irreversible loss of all brain and brainstem function. Professional medical guidelines require strict testing and the exclusion of confounding conditions before this determination is made. ( 6 )
The distinction between determining death and recording its cause is also essential. Once death is established, physicians certify the medical sequence of events that led to death for public health and epidemiological purposes. Organizations such as the World Health Organization and the U.S. Centers for Disease Control and Prevention emphasize standardized certification to ensure accurate mortality data. ( 7 ) These definitions matter deeply, shaping end-of-life care, ethical decision-making, and society’s understanding of when life has truly ended. ( 8 )
What is a Human?
Biologically, a “human” is a member of the species Homo sapiens, distinguished by a consistent set of physical and cognitive characteristics, including upright bipedal movement, advanced brain function, complex language, and the capacity for abstract thought, creativity, and moral reasoning. All living humans share these defining traits and belong to a single, unified biological species.
Genetically, humanity is marked by profound biological unity. The U.S. National Human Genome Research Institute explains that “at the base-pair level, your genome is 99.9 percent the same as all of the humans around you.” ( 9 ) This shared genetic foundation demonstrates the deep biological continuity of the human family, while the remaining variation contributes to individual differences such as physical appearance and susceptibility to certain diseases.
Anthropological research further clarifies that humans do not divide into biologically distinct racial groups. The American Association of Biological Anthropologists states that while human biological variation is real, genetic differences “are not distributed across our species in a manner that corresponds to socially defined racial categories.” ( 10 ) Race, therefore, reflects social and historical constructs rather than meaningful biological divisions within humanity.
Beyond biology, the term “human” carries ethical and legal significance. Modern human rights traditions affirm that all humans possess inherent dignity and equal moral worth simply by virtue of being human. This principle is expressed in the Universal Declaration of Human Rights, which states that “all human beings are born free and equal in dignity and rights.” ( 11 ) In this sense, to be human is not merely a biological classification, but a recognition of shared value and moral standing.
What is Pregnancy?
Human pregnancy is the physiological condition in which a new human organism develops within the uterus through an integrated relationship between the mother, the placenta, and the developing child. In clinical medicine, pregnancy is generally recognized as beginning with implantation, when the early human embryo embeds in the uterine lining and establishes the biological connection necessary for continued growth and survival. Medical textbooks describe implantation as the point at which pregnancy becomes established, allowing sustained maternal support of embryonic development. ( 12 )
A defining characteristic of pregnancy is the formation of the placenta, a temporary but highly specialized organ that mediates the exchange of oxygen, nutrients, and waste products between mother and child. The placenta also produces essential hormones, including human chorionic gonadotropin (hCG), progesterone, and estrogen, which regulate maternal physiology and maintain the uterine environment throughout gestation. Medical reviews describe the placenta as performing functions analogous to the lungs, kidneys, gastrointestinal tract, and endocrine system for the developing fetus. ( 13 )
Because the exact moment of fertilization is rarely observed, pregnancy is typically measured using gestational age, expressed in weeks and days. Standard clinical practice dates gestation from the first day of the woman’s last menstrual period, a convention that allows consistent communication and medical decision-making across populations. Professional obstetric guidelines emphasize the use of a “best obstetric estimate,” often incorporating early ultrasound, to ensure accurate assessment of pregnancy progression. ( 14 )
Pregnancy is commonly divided into three trimesters, reflecting major stages of embryonic and fetal development as well as corresponding maternal adaptations. When dated from the last menstrual period, a typical pregnancy lasts approximately 40 weeks. Throughout this time, maternal cardiovascular, metabolic, and hormonal systems undergo significant changes to sustain the developing child and prepare the body for birth. ( 15 )
What is Abortion?
In clinical and public health usage, abortion refers to the intentional termination of a pregnancy. Public health authorities define induced abortion as a medical or surgical intervention intended to end a known or suspected intrauterine pregnancy that does not result in a live birth. ( 16 ) This definition distinguishes induced abortion from spontaneous abortion, the clinical term historically used to describe miscarriage. ( 17 ) In ethical, legal, and medical discussions, abortion is often described using the terms therapeutic and elective.
Therapeutic abortion is generally used to describe pregnancy termination undertaken because of serious medical circumstances, such as significant threats to the pregnant person’s life or major bodily functions, or the diagnosis of severe fetal abnormalities. ( 18 ) These cases are widely recognized in medical ethics literature as rare and often involve complex clinical judgments regarding risk, prognosis, and available treatments. ( 19 ) Elective abortion, by contrast, refers to pregnancy termination sought for reasons other than an immediate, direct medical threat, including personal, social, economic, or relational factors. ( 20 )
Data compiled by the Charlotte Lozier Institute from state health department reporting provide insight into how often abortions are performed under medical exceptions versus elective or unspecified reasons. ( 21 ) Based on available state-level data, approximately 95.9 percent of reported abortions are classified as elective or unspecified, meaning they are not reported as resulting from circumstances such as risk to the woman’s life, rape or incest, or fetal abnormality. ( 21 ) By contrast, less than 5 percent of abortions fall into categories commonly associated with therapeutic indications, including approximately 0.4 percent reported for rape or incest, 0.3 percent for risk to the woman’s life or major bodily function, 2.2 percent for other physical health concerns, and 1.2 percent for fetal abnormalities. ( 21 ) The Lozier Institute emphasizes that these figures are drawn from a subset of U.S. states that collect and publish reasons for abortion and that nationwide reporting standards vary. ( 21 )
Across all classifications, induced abortion involves an intentional intervention to end an ongoing pregnancy prior to birth. Medical and public health literature consistently recognizes that abortion does not treat a disease of the unborn child but instead ends fetal life as a means of resolving the pregnancy. ( 22 ) This biological reality underlies enduring ethical, legal, and philosophical debates about abortion, particularly regarding the moral status of the unborn, human vulnerability, and society’s responsibility toward developing human life.
Is Abortion Murder?
Whether abortion is considered “murder” depends on the distinction between legal definitions and moral judgment. In criminal law, murder is defined as the unlawful killing of a human being with intent. Because legality is a required element, abortion is not classified as murder under the criminal codes of jurisdictions where it is permitted. This legal classification, however, does not resolve the moral question. ( 23 )
From a moral perspective, many philosophers and ethicists argue that abortion constitutes the intentional killing of an innocent human life and therefore meets the ethical criteria commonly associated with murder. This conclusion rests on the recognition that a distinct human organism exists from the moment of fertilization, a point widely affirmed in human embryology. If human life begins at conception, then abortion involves the deliberate ending of a developing human life rather than the removal of tissue or a potential being. ( 24 )
Philosopher Don Marquis argues that killing is morally wrong primarily because it deprives an individual of a “future like ours,” a future containing experiences, relationships, and personal fulfillment. Because the unborn child possesses such a future from the earliest stages of development, Marquis concludes that abortion is morally comparable to killing an adult human being. Even arguments that attempt to justify abortion by appealing to bodily autonomy, such as those advanced by Judith Jarvis Thomson, have been widely critiqued for failing to adequately account for the moral obligations owed to dependent human beings and the unique nature of the parent–child relationship. ( 25 ) ( 26 )
Legal systems themselves reflect an underlying moral tension by recognizing unborn children as victims in cases of third-party violence while simultaneously exempting abortion from homicide statutes. Scholars note that these exemptions are legal constructions rather than biological or moral determinations, underscoring that legality does not equate to moral innocence. ( 27 )
In this view, while abortion may be legally permitted in some contexts, it remains morally impermissible because it involves the intentional destruction of an innocent human life. The moral weight of that act does not depend on developmental stage, legal status, or social circumstance, but on the inherent dignity and future of the human life that is lost.
Is All Life Valuable?
Across legal, medical, and philosophical traditions, the claim that all human life is valuable is grounded in the principle of inherent dignity—the idea that human worth does not depend on ability, independence, intelligence, health, or social usefulness. Modern human-rights law articulates this clearly. The Universal Declaration of Human Rights opens by affirming that “all human beings are born free and equal in dignity and rights,” intentionally grounding value in human status itself rather than in any qualifying traits. ( 28 )
This framework is reinforced in later international agreements that explicitly reject capacity-based hierarchies. The International Covenant on Civil and Political Rights declares that “every human being has the inherent right to life,” ( 29 ) while the U.N. Convention on the Rights of Persons with Disabilities identifies “respect for inherent dignity” as a foundational principle, affirming that disability or dependency does not diminish moral worth. ( 30 ) Together, these documents reflect a broad ethical consensus that human value is intrinsic rather than conditional.
Medical ethics echoes the same principle. The World Medical Association’s Declaration of Geneva commits physicians to “maintain the utmost respect for human life” and explicitly states that considerations such as age, disease, disability, or social standing must not intervene between a physician and their duty to the patient. ( 31 ) Within mainstream bioethics, respect for life is therefore understood as universal, not proportional to prognosis or perceived quality of life.
Philosophical ethics offers a parallel justification. Immanuel Kant argued that human beings must always be treated as ends in themselves and never merely as means, grounding moral worth in dignity rather than utility. ( 32 ) Although academic debate continues—particularly over whether moral status depends on certain capacities—international law and professional ethics consistently adopt equal human dignity as the most stable and protective standard. History repeatedly demonstrates that when value becomes conditional, the vulnerable become expendable; when value is treated as inherent, protection becomes a moral obligation rather than a matter of preference.
Why Should You Care?
Abortion warrants serious moral and social attention because it is a common medical practice that intentionally ends the life of a developing human organism, a point consistently affirmed in standard human embryology texts, which state that at fertilization “a new, genetically distinct human organism” comes into existence and human development begins. ( 33 ) ( 34 ) On a global scale, abortion is widespread: major demographic analyses estimate approximately 73 million induced abortions occur each year worldwide, underscoring its significance as a societal phenomenon rather than a marginal issue. ( 35 ) ( 36 ) Abortion also carries public health implications; the World Health Organization acknowledges that while abortion is medically safe when performed according to established clinical standards, a substantial proportion worldwide has historically occurred under unsafe conditions, contributing to preventable injury and mortality among women. ( 36 ) Beyond medicine, abortion raises enduring ethical questions about human dignity and moral status. Philosopher Judith Jarvis Thomson emphasized that debates over abortion ultimately turn on how the “right to life” is understood, ( 37 ) while Don Marquis argued that killing is wrong because it deprives a being of a “future like ours,” a moral framework he explicitly applies to abortion. ( 38 ) Taken together, abortion is not merely a private choice or political dispute but a profound ethical issue involving human life, medical responsibility, and how societies choose to define protection and moral obligation at the earliest stages of human existence.
Page Citations & Notes
1. Urry, Lisa A., Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, and Rebecca B. Orr. Campbell Biology. 12th ed. New York: Pearson, 2020. Referenced for: the standard biological characteristics of living organisms, including organized structure, growth and development, responsiveness, homeostasis, metabolism, and adaptation/evolution.
2. NASA Astrobiology Program. “About Life Detection.” NASA Astrobiology. Quoted/reference point: “Life is a self-sustaining chemical system capable of Darwinian evolution.”
3. Moore, Keith L., T. V. N. Persaud, and Mark G. Torchia. The Developing Human: Clinically Oriented Embryology. 10th ed. Philadelphia: Elsevier, 2016. Quoted/reference point: the claim that a new, genetically distinct human organism begins coordinated development at fertilization.
4. President’s Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research. Defining Death: A Report on the Medical, Legal and Ethical Issues in the Determination of Death. Washington, DC, 1981. PDF. Referenced for: death as the irreversible loss of the body’s capacity to function as an integrated organism.
5. Uniform Law Commission. Uniform Determination of Death Act. 1981. Act text. Quoted/reference point: death may be determined by “irreversible cessation of circulatory and respiratory functions” or “irreversible cessation of all functions of the entire brain, including the brain stem.”
6. Wijdicks, Eelco F. M., et al. “Evidence-based Guideline Update: Determining Brain Death in Adults.” Neurology 74, no. 23 (2010): 1911–18. Neurology DOI page. Referenced for: professional neurologic criteria and testing requirements for brain death determination.
7. World Health Organization. International Statistical Classification of Diseases and Related Health Problems, 10th Revision and cause-of-death guidance. WHO ICD information. Referenced for: standardized death certification and mortality coding.
8. Centers for Disease Control and Prevention. “Medical Examiners’ and Coroners’ Handbook on Death Registration and Fetal Death Reporting.” 2003. CDC PDF. Referenced for: standardized death certification and reporting practices in the United States.
9. National Human Genome Research Institute. “Human Genomic Variation.” NHGRI. Quoted/reference point: “at the base-pair level, your genome is 99.9 percent the same as all of the humans around you.”
10. American Association of Biological Anthropologists. “AABA Statement on Race & Racism.” 2019. AABA statement. Quoted/reference point: human genetic differences “are not distributed across our species in a manner that corresponds to socially defined racial categories.”
11. United Nations. Universal Declaration of Human Rights. December 10, 1948. OHCHR text. Quoted/reference point: art. 1, “All human beings are born free and equal in dignity and rights.”
12. Sadler, T. W. Langman’s Medical Embryology. Philadelphia: Wolters Kluwer. Referenced for: implantation as the point at which pregnancy becomes clinically established.
13. Moore, Keith L., T. V. N. Persaud, and Mark G. Torchia. The Developing Human: Clinically Oriented Embryology. 10th ed. Philadelphia: Elsevier, 2016. Referenced for: placental function and maternal-fetal exchange during development.
14. American College of Obstetricians and Gynecologists. “Methods for Estimating the Due Date.” Committee Opinion No. 700 (2017). ACOG page. Quoted/reference point: use of the “best obstetric estimate,” often incorporating early ultrasound.
15. Cunningham, F. Gary, et al. Williams Obstetrics. New York: McGraw-Hill. Referenced for: standard gestational dating, trimesters, and maternal physiologic adaptation during pregnancy.
16. Centers for Disease Control and Prevention. “Abortion Surveillance — United States.” Morbidity and Mortality Weekly Report. CDC surveillance page and CDC abortion surveillance topic page. Quoted/reference point: induced abortion is a medical or surgical intervention intended to end a known or suspected intrauterine pregnancy that does not result in a live birth.
17. World Health Organization. Clinical Practice Handbook for Safe Abortion. Referenced for: distinction between induced abortion and spontaneous abortion (miscarriage).
18. American College of Obstetricians and Gynecologists. Practice Bulletin: Induced Abortion. ACOG policy/search landing page. Referenced for: therapeutic abortion in serious medical circumstances and fetal abnormality.
19. Beauchamp, Tom L., and James F. Childress. Principles of Biomedical Ethics. New York: Oxford University Press. Referenced for: the ethical complexity of rare, high-risk medical cases involving pregnancy termination.
20. Guttmacher Institute. “Reasons U.S. Women Have Abortions.” Guttmacher article. Referenced for: elective abortion sought for personal, social, economic, or relational reasons rather than direct immediate medical threat.
21. Charlotte Lozier Institute. “Reasons for Abortion Reported by State Health Agencies.” CLI fact sheet. Quoted/reference point: the page cites this source for the claim that about 95.9 percent of reported abortions are elective or unspecified in the subset of states reporting reasons, with smaller percentages attributed to rape/incest, risk to the woman’s life or major bodily function, other health concerns, and fetal abnormality.
22. Moore, Keith L., T. V. N. Persaud, and Mark G. Torchia. The Developing Human: Clinically Oriented Embryology. 10th ed. Philadelphia: Elsevier, 2016. Referenced for: the page’s summary claim that abortion ends fetal life rather than treating a disease of the unborn child.
23. Dressler, Joshua. Understanding Criminal Law. Durham, NC: Carolina Academic Press, 2018. Referenced for: the legal definition of murder as the unlawful killing of a human being with intent.
24. Moore, Keith L., T. V. N. Persaud, and Mark G. Torchia. The Developing Human: Clinically Oriented Embryology. 10th ed. Philadelphia: Elsevier, 2016. Referenced for: the page’s claim that a distinct human organism exists from fertilization.
25. Marquis, Don. “Why Abortion Is Immoral.” The Journal of Philosophy 86, no. 4 (1989): 183–202. Quoted/reference point: abortion is wrong because it deprives the unborn of a “future like ours.”
26. Thomson, Judith Jarvis. “A Defense of Abortion.” Philosophy & Public Affairs 1, no. 1 (1971): 47–66. Referenced for: bodily autonomy arguments concerning abortion.
27. George, Robert P., and Christopher Tollefsen. Embryo: A Defense of Human Life. New York: Doubleday, 2008. Referenced for: legal exemptions for abortion as legal constructions rather than biological or moral determinations.
28. United Nations. Universal Declaration of Human Rights. December 10, 1948. OHCHR text. Quoted/reference point: art. 1, “All human beings are born free and equal in dignity and rights.”
29. United Nations. International Covenant on Civil and Political Rights. December 16, 1966. OHCHR text. Quoted/reference point: art. 6, “Every human being has the inherent right to life.”
30. United Nations. Convention on the Rights of Persons with Disabilities. December 13, 2006. UN text. Quoted/reference point: art. 3, “respect for inherent dignity.”
31. World Medical Association. Declaration of Geneva. 2017. WMA text. Quoted/reference point: physicians pledge to “maintain the utmost respect for human life.”
32. Kant, Immanuel. Groundwork of the Metaphysics of Morals. Translated by Mary Gregor. Cambridge: Cambridge University Press, 1996. Referenced for: human beings as ends in themselves and never merely means.
33. Moore, Keith L., T. V. N. Persaud, and Mark G. Torchia. The Developing Human: Clinically Oriented Embryology. 11th ed. Philadelphia: Elsevier, 2019. Quoted/reference point: the page cites p. 2 for the claim that at fertilization a new, genetically distinct human organism comes into existence and development begins.
34. O’Rahilly, Ronan, and Fabiola Müller. Human Embryology and Teratology. 3rd ed. New York: Wiley-Liss, 2001. Quoted/reference point: the page cites p. 8 for the beginning of human development.
35. Bearak, Jonathan, et al. “Unintended Pregnancy and Abortion by Income, Region, and the Legal Status of Abortion: Estimates from a Comprehensive Model for 1990–2019.” The Lancet Global Health 8, no. 9 (2020): e1152–61. Lancet page. Referenced for: estimates of roughly 73 million induced abortions worldwide each year.
36. World Health Organization. “Abortion.” WHO fact sheet. Referenced for: the global prevalence of abortion and the distinction between safe and unsafe abortion as a public health issue.
37. Thomson, Judith Jarvis. “A Defense of Abortion.” Philosophy & Public Affairs 1, no. 1 (1971): 47–66. Referenced for: debates over how the “right to life” is understood.
38. Marquis, Don. “Why Abortion Is Immoral.” The Journal of Philosophy 86, no. 4 (1989): 183–202. Referenced for: abortion as depriving a being of a “future like ours.”
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