What Is a Human Being?

Key idea:
The sense of personal identity appears to be more strongly connected to the functioning of the brain than to individual parts of the physical body.

As described above, the human being consists of all kinds of organs, systems, and limbs. If one organ is removed, does the person remain the same, or do they become, in some sense, a slightly different person? How do we determine what a person is, and what determines being human? Is it determined by behavior or by appearance?

If a person receives an artificial hip, does that change the person? If the person is known as an Olympic athlete, the replacement may affect their performance as an athlete, but do we then also consider them to have changed as a human being? The same applies when the heart is replaced, and so on. How many body parts and organs can we replace before someone is no longer the same person?

If something in the brain is changed through surgery or otherwise, this generally appears to be capable of causing a greater change in the person. It therefore remains dependent on what we regard as the defining characteristic of that person.

An important difference between humans and many other animal species is the extent to which the human brain enables certain forms of abstract thinking, language, planning, and self-reflection. Humans can use their brains to think about the future and the past, calculate and write, and communicate with other people through understandable sounds.

Other animals also possess forms of communication, planning, memory, and problem-solving ability, but human language and abstract thinking have reached an exceptional level of complexity. All of these abilities are initially directed by the brain and are subsequently carried out with the help of various organs: arms, hands, voice, eyes, and so on.

Important characteristics include:

• abstract thinking
• language
• reflection
• planning

As an example, we can consider Stephen Hawking, the British physicist, who developed amyotrophic lateral sclerosis (ALS), which progressively impaired his muscle control while his cognitive abilities remained largely intact. In this case, Hawking was nevertheless regarded as the same person he had been before the disease, apart, of course, from his physical characteristics. Could this be because the defining characteristic of Hawking was his capacity for thought?

Would this have been different in the case of Usain Bolt, the Jamaican sprinter, if his cognitive abilities had declined to a very low level while his sprinting performance had remained unchanged?

These two examples show that we cannot simply derive personal identity from physical performance. In Hawking's case, the body became increasingly less capable of carrying out his intentions, while we continued to regard him as the same person. With Bolt, we can imagine the opposite situation: an almost completely intact body, but a profoundly changed capacity for thought. Would he then still be the same person?

All things considered, personal identity appears to be strongly connected to the functioning of the brain. Or, as the title of Dick Swaab's book puts it: We Are Our Brains.

But this very idea raises a further question. If personal identity is so strongly connected to the brain, can a person be reduced entirely to their brain? Or do memories, personality, experiences, and the continuity of consciousness also play a role?

When considering this question, an anecdote told by a philosopher comes to mind. It goes as follows:

An elderly man, so physically weakened that he does not have long to live, but whose cognitive abilities remain excellent, has a conversation with a young athletic man. He says to the young man:

“I do not have long to live, but you are still young, handsome, athletic, and have your whole life ahead of you. You are almost perfect, but the only drawback is that the cognitive abilities you were born with are not particularly impressive. Since I am at the end of my life, I no longer have much use for my brain. I therefore offer to have my brain transplanted into your head and yours into mine. Your quality of life would then improve considerably, and for me it no longer matters.”

We do not know what the young man replied, but it is an interesting thought experiment that raises intriguing questions.

If the old man's brain were placed inside the young man's body, who would then be the old man and who would be the young man?

• Where does identity reside?
• What makes someone “themselves”?

And perhaps even more fundamentally: what does it mean that this person, however clearly we try to define them, is ultimately mortal?