A long, long time ago, in a country far, far away, a wisdom lover was wondering how things could be defined meaningfully: in a way that would be sound (what is defined corresponds to what we want to define), complete (all the aspects of the thing we want to define are accounted for in our definition), and actionable (to be useful, this style of definition should be reusable). This country far, far away was ancient Greece, the name of this wisdom lover was Aristotle, and he structured definitions with four “causes” – one about the constituents of the thing we want to define (the material cause), one about what has to be done to these constituents to make this thing (the efficient cause), one about the methods used to operate on these constituents (the formal cause), and one about what this thing is for (the final cause).
Aristotle’s four causes are stated as follows:
The sentence “To make a dish, a cook operates over the ingredients according to the recipe.” includes all four causes:
The sentence “Using a toothbrush, Michael Scofield unhinges the prison door to escape.” also includes all four causes:
Anton: Wait. Michael Scofield isn’t an actor, he is a character. Wentworth Miller is the actor who play this character.
Pablito: That is correct. I just checked on Wikipedia.
Alfrothul: I am reasonably sure that it’s not the point.
Dana: Right. You guys are crossing levels of reality. Can we move on to the next example?
Anton: Sure.
Ditto for “My program computes a function over discrete data to predict the weather.”:
Ditto for “My recognition algorithm for infinite strings operates in linear time.”: the goal is to recognize, the action is an algorithm, this algorithm operates on infinite strings, and methodologically it proceeds in linear time, i.e., in a time that is proportional to the size of the given strings.
Halcyon: Is this an invitation for critical reading or what?Mimer: Yup.Dana: They mean strings that are arbitrarily long.The fourth wall (courteously): Mind your step.Dana: Thank you.
Anton: So we need to do what?Mimer (patiently): You need to write several sentences and several paragraphs.Alfrothul: Several sentences and several paragraphs about what?Mimer: Any topic you fancy.Dana: And we write them how?Mimer: In a way such that Aristotle’s four causes are visible.Pablito: Er... Why do we need to do this?Mimer: To acquire control over your narratives. “I code, therefore I don’t need to think” is no way to go.René Descartes: This is getting interesting. Do you guys need a chairperson?Mimer: Mr. Descartes, thanks for stopping by!
What is the point of the little dialogue in Exercise 01?
Sometimes, one cause is enough:
Material cause:
Question: What is this rock?
Answer: Granite.
Anton: What is this liquid?Alfrothul: Helium.Halcyon: This is so cool!
Question: What is this liquid?
Answer: Water.
Efficient cause:
Question: What is this painting?
Answer: A Picasso.
Question: What is this car?
Answer: A Renault.
Formal cause:
Question: What is this game?
Answer: Chess.
Question: What is this movie about?
Answer: A love triangle.
Question: What is this mathematical figure?
Answer: The lemniscate of Bernoulli.
Final cause:
Question: What is a pen?
Answer: Something for writing or drawing.
Question: What is a ruler?
Answer: Something for drawing straight lines or measuring.
Question: What is a pair of compasses?
Answer: Something for drawing circles.
Aristotle’s four causes address aspects of a thing. They can be used to define this thing. They might seem quaint at first, but when encountering a new concept, it is surprisingly fruitful to characterize the four causes of this concept.
More broadly, the present lectures notes follow Aristotle in that they systematically proceed from what is known towards what is unknown (yet), with room enough to grow, freedom enough to make one’s own mistakes, and time enough to learn from these mistakes, without grade penalty.
Mance Rayder: Sounds pretty good to me.Halcyon (squaring his shoulders): What he said.