One of the most important questions human beings ask is, "Why?"
Following Aristotle, Saint Thomas Aquinas thinks there are four ways to answer this
question, traditionally called the four causes.
Think about a wooden dining room table.
Why is the table this way?
Now, the first answer might refer to the carpenter who made the table.
He is the efficient cause.
In general, the efficient cause is the agent or thing that brings something about.
This is what most people think of when they hear the word cause.
In fact, the word efficient comes from the Latin term for making.
The efficient cause is what makes the thing or the effect.
The second answer to this question, "Why is the table this way?" is the material cause
of the table--wood.
This might make a big difference in the quality and properties of the table.
Mahogany is elegant, while pine is more basic; bamboo is light, while oak is heavy and durable.
But there's a third reason why the table is this way.
It's the form, or the structure, or the design of the table.
This is what we call the formal cause.
Now by form, Aquinas means more than the physical shape of the thing; he's referring to the
essence or the nature of the thing, what makes it the kind of thing it is.
Now, Aquinas thinks that all natural things have an intrinsic form or essence.
The form, essence, or nature of lion is in a certain sense why a lion is the kind of
animal it is, and this form or nature is really in the lion.
Now in addition to this, Aquinas identifies some forms that are outside, or extrinsic
to a thing.
He calls these ideas, or an exemplar.
Think, for example, of the table's design.
It starts in the carpenter's mind as he thinks about what he's going to make, and this idea
then guides his activity.
He doesn't saw wood at random, but he follows his plan.
In fact, it's a kind of metaphysical law that every act of efficient causality is guided
by some formal causality.
Now this idea, or exemplar, also becomes the measure of the carpenter's work.
A novice carpenter might say, "Well, this table just didn't turn out the way it was
supposed to," and by that he means either that his activity of making the table, his
efficient causality, somehow went wrong, or that the matter was somehow defective so that
he didn't fully realize the idea he had of the table.
This brings us to the fourth reason why the table is the way it is.
This fourth cause is extremely important, and it's called the final cause because it
refers to the ultimate end or reason for the thing.
What is a table for?
In this case, dining.
We can't fully explain something unless we know what it is for.
Now, of course, the carpenter might've had other reasons for making a table, like earning
money, but that human purpose falls outside of the intrinsic end or reason for the table.
The final cause of the table itself, properly speaking, doesn't refer to the carpenter's
personal motive, but to what a table is for.
Now, Aquinas thinks that these four causes can be applied by way of analogy to everything
in creation, and so they offer a very powerful way of explaining the why of things.
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