Ghost in the Shell, for those of you who don’t know, is a TV show in which several of the characters are complete cyborgs. Their only remaining biological part is their brains. They can swap damaged parts for new ones when needed, and even control their bodies remotely at times. This raises the interesting question of how do we define what to be human is? Obviously we could be sticklers and insist that only someone with a biological brain could be human, but this definition seems too limited. After all, the characters have given up most of their biological parts, what’s one more?
We might be tempted to call human anything that looks and acts human. Certainly we have a hard time emphasizing with things that don’t look like us. But is it right to put so much emphasis on form? In one of the show’s episodes the characters encounter a wealthy businessman who is also a cyborg. Unlike the characters, however, his body is a small box-like thing. Initially the viewer may not think he is more than a robot, since he appears so strange. But, once he engages in conversation with the characters, it is clear that he is as human as they are. He is energetic, quirky, opinionated, and undeniably human.
So our definition of being human is acting human? This seems reasonable to me, but I must stress that acting human is a narrower category than it might seem. To act human is not simply to be conscious, since many animals are conscious. Nor is it to be intelligent; computers are intelligent, but they aren’t human. I think it unlikely that even something that was both conscious and intelligent would necessarily act human. What distinguishes human behavior from the behavior of any conscious intelligence is our social connections with other people. Specifically we try to understand other people and to form relationships with them. By this I don’t mean that to be human is to be nice or friendly. Some people try to understand other people simply to be able to predict their actions, and thus outfox them. Likewise, for some people, the only relationship they seek with others is one of conflict.
I admit that this definition of human is still rather broad, and may label as “human” species that have no biological or historical relation to us (that is if aliens do exist somewhere out there). Likewise it is a definition that is by its nature somewhat vague. Certainly it is possible under this definition to be more or less human. I don’t see these points as a weakness in the definition, because I approach humanity as a natural kind that is a subset of conscious-intelligences, and thus I expect it to include more than the people we currently know, since we really have only been exposed to one type of conscious intelligence so far. It is certainly possible to form a definition of human as a conscious intelligence that is, or was at one, point biologically human, but I think that such a definition is too narrow by far.