What is a Human, Really? Thinking about Definition via Aristotle

Posted on March 21, 2011 by Santi Tafarella

If your definition of a word is to be any good, Aristotle was the first to notice that it should say something general and something specific. Aristotle designated these two components the genus and species of a definition. Thus you might define human this way:

A human is an animal (genus) that is rational (species).

Or you could simply say:

Humans are rational animals.

Aristotle’s species component of a definition is sometimes referred to by the Latin word, differentia. And so, in definition, we have a general statement about a word accompanied by a differentia. Hence this too might be considered a definition of human (though perhaps not a good one):

A human is an animal that laughs. 

The reason a laughing animal is not quite as good a definition of the human as a rational animal is that one seems more essential to being human than the other. Or, at least, you could argue this (but don’t try it with someone who is British).
In any case, in seeking a good definition for a word, we want to identify, not just its unique properties, but its most essential qualities (and to foreground those). Aristotle’s own definition for the human was “political animal.” He believed that the most essential differentia about humans was their cultural behavior—their collective life in the polis (the city).  
But in defining something, we might also wish to say something a bit less obvious and concise, and be a tad more elaborate:

Humans belong to the small group of self-aware social mammals that includes chimps and dolphins. 

That’s a pretty clear answer to the genus question: humans are broadly or narrowly located within the hierarchy of living things, and most specifically within the kingdom of animals (or even more specifically, within the group of mammals that are self-aware and social). But notice that there’s no differentia on this definition yet.
Now for the differentia—the “species” designation. What distinguishes, in an essential manner, humans from other self-aware social mammals? In answer to this we might conclude the following: humans are uniquely characterized by their ability to reason, to speak, and to extend their influence and control over their environments via tools.
So this brings us to a pretty good definition for what it means to be human:

Humans are self-aware social mammals generally possessing the ability to reason, speak, and use complex tools.