When does a person's life begin?
The question of when a person’s life begins is logically, biologically, and philosophically complex. To approach this question, we first must to clarify what we mean by "person." Three definitions of person you may have heard before are “human being,” “human organism,” and “human organism with a mind." In casual conversation, the choice of definition may not be crucial; however, in formal conversation where people's well-being and freedom are at stake, it is essential to use the most accurate definition.
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"Human Being"
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If you heard, “Aunt Sue is a human being. She deserves to be treated with respect,” you’d probably nod along in agreement. In casual conversation, emphasizing that someone is a “human being” is a way to highlight their importance. But is “human being” a good formal definition of person? Surprisingly, no. When we apply logical syllogism to this definition, we uncover a problem: all living human cells, from skin cells to muscle cells to bone cells, etcetera, are technically “human beings.” Using the definition “human being” produces the technical result that a single human skin cell deserves the same respect as Aunt Sue.
The syllogism goes like this:
All living cells are living things.
All living things are beings.
Therefore, all living cells are beings.
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Then we apply human categorization, and we can see:
All living human cells are human beings.
If we formally use “human being” as our definition of person, the result is that we formally grant personhood to all living human cells, from skin cells to muscle cells to bone cells, etcetera.
This clearly isn’t what we intend to happen from our definition of person, so “human being” is not an appropriate formal definition.
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"Human Organism"​
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Next, let’s examine the “human organism” definition. While this definition avoids the problem of classifying individual human cells as people, it presents its own challenges when subjected to deductive reasoning and modus tollens.
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Modus tollens operates like this:
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If P, then Q.
Not Q.
Therefore, not P.​
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When a statement of the form "If P, then Q" is true, then the inverse "If not Q, then not P" must also hold true.
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Consider the statement: "If we can save either a large group of people or a small group of people, with no extraneous variables affecting the decision [P], then we save the larger group [Q]."
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This statement is always valid when there are truly no extraneous variables and when we accurately define person to determine how many persons are in each group.
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Some examples of extraneous variables include:
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Poor health: May lead to a preference for saving healthier individuals.
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Ageism: An age gap could skew preferences toward those with more life expectancy.
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Intelligence/talents: Could bias the decision toward those deemed more valuable to society.
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Established relationships: Emotional connections might influence a rescuer's choice.
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End-of-the-world scenarios: May lead to saving the people (or things) considered more useful in preventing the end of the world—because without the world everyone ends up dead anyway.
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We can use the statement from above to test the "human organism" definition of person. The terms "fertilized egg" and "newborn" fit the definition, with less than a year of age difference, thus minimizing concerns about age bias or extraneous variables. Now consider the following:
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If we face a tragic scenario where we can save either a large group of fertilized eggs or a small group of newborns, then which group do we save?​​​​​​​​​​​​​​​​​
Pictured Left: Fertilized human egg photographed at 20x magnification (Shutterstock). Pictured Right: Newborn (Canva).
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In reality, most people would save the small group of newborns rather than the larger group of fertilized eggs. Since we do not save the larger group, modus tollens and deductive reasoning lead us to conclude that "human organism" is inadequate for defining person.
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Being a person requires more than being a human organism. Newborns have it. Fertilized eggs don't. But what is "it"? And at what developmental stage does "it" emerge?
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At first, some people may guess the "it" is heartbeats, but this would exclude people suffering from cardiac arrest from being considered persons. Others might guess the "it" is reflexes, referencing the quickening, which is the moment a pregnant woman first feels fetal movement. However, this guess falters because even deceased bodies can exhibit reflexes. Another guess for "it" is viability, the ability of a living thing to survive. But consider examining a living thing's viability and not already knowing whether or not the living thing is a person. Does the fact that a living thing is deemed viable assure us that it is a person? No. Viability doesn’t tell us if a living thing is a person; thus, it makes little sense to use viability in a definition for person.
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"Human Organism with a Mind"​​​​​
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The third definition—the most promising one—defines a person as "a human organism with a mind," where a mind is the ability to think thoughts and feel emotions, or more technically, a brain with neuro-infrastructure for thought and emotion.”​
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Recall from the introduction that defining "person" is a logical, biological, and philosophical challenge. So far, we have considered logic and biology, but not philosophy. From the perspective of philosophy, personhood requires mental and moral capacities. If a human organism lacks the brain infrastructure to think and feel emotions, then it lacks all mental and moral capacities and thus is not a person. This explains why newborns are persons while fertilized eggs are not. Newborns have brains with the ability to think thoughts and feel emotions. Fertilized eggs don't have brains.
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Consciousness and Memory
A pertinent question arises: "Does this last definition include unconscious people?" The answer is yes. People who are sleeping, unconscious, or in a coma still have minds. Consciousness exists on a spectrum, from fully aware to brain-dead. A brain-dead individual, unlike someone merely unconscious, no longer has a mind, and thus is no longer a person. When someone is unconscious or in a coma, their mind is damaged but still there, and when someone is sleeping their mind is recharging.​​
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Another question arises: "Does this last definition include people with dementia?" The answer is also yes because for memory issues to exist, a mind must exist.
The bottom line is that once a human organism develops a mind, the mind continues to exist until brain death.​
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Non-Human Personhood
Another question asks, “What about beings with minds that aren’t human? Is it fair to deny them personhood just because they’re non-human?” Intelligent species like dolphins and elephants exhibit thought and emotion and possess distinct personalities. Why do we deserve personhood and associated rights and yet they do not? Similarly, as artificial intelligence (AI) advances, it may acquire the ability to think thoughts and feel emotions. Would AI then not qualify as a person? And what about the possibility of extraterrestrial lifeforms with minds? Would they not scoff at us, “Narcissistic humans, they used to believe the universe revolved around their planet, and they still believe that personhood revolves around their species!”
A central understanding of personhood is that being a person means being a part of a moral community, having the moral right of self-determination, and bearing the moral responsibility of treating all persons with respect. Can we trust thinking and feeling non-humans to participate in our moral community? Can any species that lacks literacy and complex communication be expected to understand rights and responsibilities?
All thinking and feeling beings deserve equitable and respectful treatment from persons, but the issue of non-human personhood remains. In the spirit of open-mindedness, we therefore emphasize that “a human organism with a mind” is a workable definition for “human person” but not for “universal person.” To address the abortion debate in the United States, the “human person” definition suffices because the only people involved in this social reckoning are human.
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The Role of the Brain in Human Personhood
For human persons, the ability to think thoughts and feel emotions arises from within the brain. When your brain ceases to function—that is, when it ceases to able to think thoughts and feel emotions—your life as a person ends. Likewise, when your brain gained the ability to think thoughts and feel emotions, your life as a person began. In order for the ability to think thoughts and feel emotions to exist, a minimum level of brain infrastructure must first exist.
Image Credit: TheVisualMD/Science Source
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Extensive study and research have been dedicated to mapping the timeline of human brain development and identifying which brain regions are essential for thought and emotion.
There is a part of the brain called the thalamus, and it is located on the top of the brainstem. The thalamus acts as the gateway for all sensory information (except smell) to reach the cerebral cortex, where thoughts and emotions are processed. Additionally, the limbic system works alongside the cortex to give rise to emotions. Until the thalamus is connected to the cortex, it is not possible for a brain to have thoughts because there is no sensory input about which to think! Similarly, until the thalamus is connected to the cortex, it is not possible for a brain to have emotions because there is no sensory input about which to feel.
To illustrate this point, consider a sensory deprivation tank. If you were to spend time in a sensory deprivation tank, during that time you would be able to think thoughts and feel emotions, but they’d only be based on your memories of past sensory experiences. If a developing brain has yet to develop the infrastructure necessary to receive sensory input, then not only does it have no access to incoming sensory input, but also it has no prior memories of any sensory input about which to think or feel. Only after thalamocortical fibers connect a fetal brain’s thalamus to its cortex can it be possible for that brain to have the ability to think thoughts and feel emotions. This connection occurs between 23 to 25 weeks gestation, indicating that a new mind begins to exist at 23 weeks gestation.
Prior to thalamocortical connection, a fetus is an empty vessel. The moment that connection occurs, the fetus evolves from unborn body to unborn baby, gaining the rights and responsibilities of emerging personhood.
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In conclusion, the life of a human person begins at 23 weeks gestation, when a new mind comes into existence. This understanding clarifies ongoing discussions surrounding abortion, allowing us to navigate this intricate moral landscape with greater insight.