Is there such a thing as human nature or is that just a conventional idea?
In ancient Greek philosophy, investigation of nature actually begins with a reflection
on change.
Realities around us are constantly changing.
So from this observation, Heraclitus postulated that there is nothing constant in the world.
Everything is in flux.
You cannot step in the same river twice.
Therefore we cannot talk about there being stable natures or properties of things.
Continuity is only apparent, and the notion of nature is merely conventional.
From the opposite vantage point, Parmenides unabashedly deny that there is any real change
happening in the world.
On this view, what we call change in the world is just illusory.
The ultimate bedrock of reality is unchanging and static.
This view also seems to make the various natural things around us unreal since they are all
subject to change.
Now against both these extreme positions, Aristotle argued both that there is real change
in the world against Parmenides (since it's something obvious to our senses), but also
that there's continuity in things that are subject to change against Heraclitus.
In the things that were before there persists the things that are now.
This is where you start to get the idea of an essence or nature of a thing--that which
endures amidst the change, that which is in that which was.
So there are constants that remain.
Think about an adolescent human being that used to be a baby; that baby used to be an
embryo. And then you look at that same human being 10 years later, and it's an adult, or
then later and it's an older person.
But there's something that remains in and through all of that, and it's more than just
the name of the thing.
It's the nature of the thing.
The natural kind is a principle of continuity and development.
Aristotle describes nature as a principle or cause of motion and rest in that to which
it, the nature, belongs primarily and per se.
That means the nature is the thing that endures, but also the thing that helps organize all
the change happening in the thing.
Because things have nature, we can rely upon them to act in predictable and identifiable
ways, and that's the basis of science as well as common sense.
It's partly for this reason that certain features of the intelligible universe are described
in terms of laws of nature.
Namely, things operate with a kind of persistence because of the type of thing that they are.
So though some natural things may fail to achieve the perfection or to act in a way
that accords with their perfection, yet we can basically rely upon things to act in predictable
and stable ways always or for the most part.
This metaphysical observation lays the groundwork for the natural law.
There's a law at work in nature which inclines unto flourishing or perfection.
It's very evident in animals.
Animals seek their own good through nutrition, growth, and reproduction.
Those are predictable features of their nature, and they allow us to organize our knowledge
according to stable laws of nature.
And in the rational animal, there are operations of intellect and will of human beings who
seek their own good through life in society, through virtuous friendships, and the search
for the truth.
Nature gives rise to inclinations and from these natural inclinations, we can begin to
seek the basis for the precepts of the natural law, ethical norms that allow human beings
to tend to the proper good of man.
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