Being Human: How Should We Define Life and Personhood?

People often use the phrase, I am only human, as an excuse for making mistakes. We all know and understand what it means to be human. Yet, when it comes to defining what being human means in the world of bioethics, the question does not quickly yield a simple answer. We do not want, however, to make a mistake in finding the right answer to this question.

Our answer will shape our view on many important issues: scientific research on embryos, reproductive technologies, abortion, end-of-life decisions, care of patients with brain damage, and policies on animal rights, genetic engineering, and artificial intelligence. What does it mean to be human is at once a biological, theological, and ethical question.

While students often debate the question on college campuses and discuss it in seminaries, the question is more than a matter of academic interest. The question is relevant to everyday ministry situations pastors face. In hospital visitation, pastors encounter family members of patients struggling with decisions for care of preterm infants, car accident victims with brain damage, and the terminally ill. In the counseling office, pastors answer questions from couples about choice of birth control methods and reproductive technologies. In the pulpit, pastors address the difficult moral issues facing our society, such as how to protect the young, the disabled, and the elderly. To define what it means to be human as it relates to bioethical decisions, let us examine the scientific, biblical, and ethical answers to this question.

How Biology Defines Life

To understand what it means to be human, let us start with defining what constitutes human life. Science defines life as the possession of self-sustaining biological processes. This definition distinguishes the living from the dead (those whose self-sustaining processes have ceased) and from the inanimate (objects who lack such processes). Self-sustaining biological processes include homeostasis, organization, metabolism, growth, development, adaptation, response to stimuli, and reproduction. Homeostasis refers to the ability of a cell, or the entire body, to maintain a state of internal balance by adjusting its physiological processes. Organization means the functional unity of a living organism that creates integration and control between all the parts of the organism. Metabolism involves the consumption of food and the production of waste.

Biology defines life at the cellular level. The cell is the smallest unit of life. Every living thing is comprised of cells. An organism made up of only one cell, such as an amoeba, is alive as much as an organism made up of an estimated 10 trillion cells, such as a human being. Infectious agents such as viruses — which cause diseases such as the common cold, the flu, polio, and AIDS — and prions — which cause diseases such as kuru and Creutzfeldt-Jakob disease — fall short of the definition of life. Viruses and prions cannot undergo reproduction or metabolism without help from the cells they are infecting. Scientists, however, considered infectious agents such as bacteria as alive because bacteria are single cell organisms.

A single cell is alive. A cell is human if the genetic blueprint of the cell is human DNA. Techniques of cellular biology make it possible to take cells from human organs and grow them indefinitely in laboratory culture. The cells are alive and the cells are human. Human cells in laboratory culture, however, are not human organisms.

An organism refers to an entire living entity. Some organisms, such as bacteria, consist of only one cell. Other organisms, such as humans, start as one cell but develop to become multicellular, with many specialized cells all working together to maintain the life processes of the whole organism. So scientists do not consider human cancer cells taken from a cervical tumor that grow in a laboratory dish human organisms because they are only one small part of an entire human organism.

Scientists do, however, consider a human embryo that has been growing for 3 days in a laboratory dish and is now comprised of approximately eight cells, a human organism. These eight cells of a human embryo 3 days after fertilization possess organization and function as a unit capable of further development. These cells represent the entire human organism, not just a part of an organism like the human cancer cells in laboratory culture. Although these eight cells are not yet differentiated into the specialized cells that are present in a fully developed human, these cells have the capacity to give rise to every specialized cell that will be needed as development progresses.

Five days after fertilization, the human embryo will be shaped like a hollow sphere and contain from 70 to 100 cells. The term for the human embryo at this stage of development is a blastocyst. The blastocyst is the stage of human development when the embryo attaches to the wall of the uterus, a process scientists call implantation. This typically occurs 7 to 10 days after fertilization. This adhesion to the wall of the uterus allows the developing embryo to receive the oxygen and nutrients from the mother to allow further growth and development.

An embryo in the earliest stages of development is a living, multicellular organism with a genetic code unique from the genetic code of the mother and father of that embryo. An embryo that develops from the fertilization of a human egg and a human sperm is a human embryo. So, an embryo is a human life. With the right conditions for further development, a healthy human embryo will develop the secondary characteristics of self-awareness, rationality, and capacity for language that collectively distinguish human beings from other living organisms.

How the Bible Defines Human Beings

While the Bible is not a textbook on developmental biology, the Bible contains information that defines what it means to be a human being. In Genesis 1:27, we read, “God created man in his own image, in the image of God he created him; male and female he created them.” As a result of God making man in His image, God gave man special status and dominion over all other animals (Genesis 1:26). The Bible gives the reason for the moral seriousness of murder in the fact God made man in His image (Genesis 9:6). Being made in the image of God connotes that human beings have intrinsic moral value based on whom we are instead of extrinsic moral value based on certain functions and capabilities we possess.

The Bible also teaches that human beings have a spirit as well as a body. James states that the body apart from the spirit is dead (James 2:26). When Paul teaches about the Resurrection, he distinguishes between the spirit and the body (1 Corinthians 15:44). If human beings have a spirit as well as a body, then a human being has value beyond the condition and developmental stage of his body. The identity of a human being involves more than just the state of the physical body or the measure of mental capacity.

The Bible demonstrates that God cares for all human life, regardless of capacities. Psalm 139:13–16 shows that God knows us even at the earliest stages of embryological development, before our organs have formed and our cells have differentiated. In demonstrating His providential care for the developing child within his mother’s womb, God affirms the dignity of human life before birth. In addition, this passage supports the concept of human beings having intrinsic value bestowed on them by their Creator that is not contingent on attaining a certain developmental stage or acquiring certain functional abilities.

God’s call on the lives of the prophet Isaiah (Isaiah 49:1) and the prophet Jeremiah (Jeremiah 1:5), as well as the apostle Paul (Galatians 1:15), originated before birth while they were still in their mother’s womb. In Luke 1:39–44, the Bible tells of John the Baptist at 6 months’ gestation in his mother Elizabeth’s womb leaping for joy as Mary, carrying the developing Messiah within her womb, came to visit. These Scriptures support the concept of an individual having personal and moral continuity from the very beginning stages of human life within the womb to adulthood.

How Bioethics Addresses Personhood

When bioethicists struggle to answer the question of what it means to be human, they are not trying to determine what constitutes human life. Biology clearly defines human life as beginning when the fertilization process is complete and a new, genetically unique organism comes into being. Bioethicists attempt to answer the question of personhood, or when a human life attains moral standing. Philosophers and ethicists have proposed a number of thresholds for determining when a human being becomes a person.

The genetic view of personhood believes that a human being is always a human person, thus personhood comes at conception. The next milestone for moral standing comes 14 days after fertilization, when the process of gastrulation begins. The mark of this stage is the appearance in the embryo of the primitive streak, a precursor of the spinal column. Bioethicists call the perspective that personhood begins when the process of gastrulation commences the embryological view of personhood.

Gastrulation is the process when the three germ layers of the body form (cells differentiate into three categories) and establish the basic body plan. In humans, gastrulation occurs after the embryo implants into the uterine wall of the mother. Before gastrulation, an embryo can split and become identical twins. After gastrulation, an embryo is an ontological individual and can no longer form more than one human being. Regulations in many countries, including Great Britain, treat 14 days after fertilization as the limit for conducting scientific research on embryos.

Those who reject gastrulation as the important milestone for defining personhood argue that twinning does not alter moral standing: one human life has simply become two human lives. Since at least one human life may begin after fertilization, fertilization is the important milestone in determining personhood, not gastrulation.

Some people feel that the appearance of blood in the embryo marks the attainment of personhood. These people use the teaching in the Bible that “the life of a creature is in the blood” (Leviticus 17:11) to define the point at which research on developing embryos becomes unacceptable. Soon after gastrulation is complete, specialized cells such as blood cells form and the embryonic heart starts beating around 21 days after fertilization.

Another view on personhood is the neurological view. Doctors define brain death as the loss of the pattern produced by a cerebral electroencephalogram (EEG). Those who hold to this argument reason that if we base life and death on the same standard of measurement, then personhood starts when a fetus acquires a recognizable EEG pattern, which occurs about 24 to 27 weeks after fertilization. The argument against this view on personhood, however, is that the lack of brain activity at the end of human life is not the same as the lack of brain activity at the beginning of human life.

The brain dead individual has permanently lost the ability to function as a human being, with no hope of reviving brain waves. Although an embryo may not have reached the stage in development at which we can detect brain waves, a healthy developing human embryo possesses the inherent capacity to have these brain waves at some point in the future. The lack of brain waves in a healthy human embryo is only a temporary condition. Most important, the developing embryo is able to integrate his or her basic life functions as an organism, which the brain dead individual can no longer do.

Scientists base the technological view of personhood on when the developing fetus becomes viable (able to live outside the mother’s womb). The most important factor in whether or not a fetus is viable is not neurological development, but maturation of the lungs. Advances in medical science make it possible for a premature baby to breathe after only 25 weeks of gestation, prior to when functioning lungs have fully developed.

People sometimes base laws related to when a person can legally abort a fetus on this view of human personhood. But advances in medical technology have moved the point of fetal viability to earlier points in gestation, thus the point at which a fetus becomes a person changes as technology improves. Real biological limitations on when breathing is possible exist, however, regardless of technological advances. For this reason, we can also call using viability to determine personhood an ecological view of personhood, since personhood rests with the ability of the developing human being to exist apart from biological environment of the mother.

The physiological view of personhood argues that personhood commences at birth, when the baby has his own functioning circulatory, respiratory, and alimentary system independent of the mother. The traditional Jewish view confers personhood during childbirth, when the head emerges from the birth canal.

Another way to view personhood is in relation to the functions of the neocortex of the brain: rationality, self-awareness, and relationship with others. Many consider this approach to defining personhood as the postmodern view. This view considers the essential functional capacities that set humans apart from other animals. Yet, humans do not fully develop these capabilities until some time after birth, during toddlerhood.

When considering the criteria for personhood, we would do well to ponder if we should reduce personhood to a set of capacities or a biological marker. Should moral significance come from who we are or from the functional capabilities we express at a given moment of our existence? From a biblical viewpoint, does the image of God refer to an intrinsic value that human beings possess or to an extrinsic value measurable by medical science and capable of being lost due to damage of the physical body? Is the natural inherent capacity for self-awareness and a free will sufficient to make us persons, even if disability or disease limits the expression of these functions?

Finally, from a pastoral perspective, the use of the concept of personhood to exclude people rather than include people should raise red flags of caution for us. Are we separating human persons from human beings to limit our moral responsibility as a society? In Luke 10:29, an expert in the Law asked Jesus, “Who is my neighbor?” in an effort to justify himself as having fulfilled his duty to love his neighbor as himself. He was hoping the Lord would provide him with a definition of neighbor that would limit his moral responsibility to his fellowman. Instead, Jesus told the Parable of the Good Samaritan, broadening the moral responsibility required of the expert in the Law. Perhaps, in keeping with the message of this parable, we need to be wary of a too narrow definition in answer to the question, “Who is a person?”

Christina M.H. Powell