What counts as explaining something?

A cup and several whys

Return to the potter who shapes clay into a cup. Asked why there is a cup on the table, she might describe the clay, explain how she shaped and fired it, or say that she wanted something to drink from. Asked what makes it a cup, she might point to its hollow form and the way it holds a drink. All these answers concern one object, but each does different work.

The previous lesson separated an orderly arrangement from a just one. Another distinction matters now: explaining how something was produced does not always explain what it is or what it is for. Aristotle, who studied in Plato’s Academy, makes these differences central to inquiry. In his Physics, the study of nature covers living things and change in general, a far broader subject than the one we now call physics. [1]

Four ways to answer

Aristotle distinguishes four causes, each of which identifies something an explanation depends on. Because he is asking what makes things be and change as they do, his word “cause” reaches further than an earlier event that triggers a later one. [1]

• The material cause answers what something is made from: the clay that is shaped and fired into our cup.
• The formal cause answers what makes it the kind of thing it is: its organization as a vessel that can hold a drink.
• The efficient cause answers where the change comes from: the potter exercising her craft as she shapes and fires the clay. “Efficient” here does not mean quick or economical.
• The final cause answers what the making is for: drinking from the cup. An end, in this sense, is the aim or function that helps explain the process.

These are roles in an explanation, not four events in sequence. Naming the potter still leaves us asking how she made the cup, and what matters is her skill, not her hair color: Aristotle asks for the cause relevant to the question. One thing may fill more than one role, and a particular event need not call for all four kinds of answer. [1] [3]

What makes this a thing?

The clay doesn’t explain everything about the cup, since it could have become a tile instead. What tells us what this material has become is its form, and form can include organization and function; it need not mean merely the outline we see.

This brings us back to being, the question of what it is for something to be. In the Metaphysics, Aristotle distinguishes a thing from its qualities and activities: being healthy requires something that is healthy. Substance names what exists as the thing to which those qualities and activities belong. A living plant is a good starting example, since its greenness and its height belong to it. In this sense “substance” does not simply mean a material, as it does when we call clay a sticky substance. [2]

Aristotle then asks whether matter, form or the combination of the two best explains what makes something a substance, and he treats form as a cause of the material’s being a definite thing, not a heap. This is an inquiry; the word “substance” does not solve the problem by itself. In these passages we can distinguish a natural thing’s form from its matter when we explain it, but the form does not exist apart from its matter. Aristotle’s form should therefore not be confused with the separate Platonic Forms of lesson 21. [1] [2]

Being able and actually being

Before the potter begins, the clay is capable of becoming a cup under suitable conditions; it is not a little cup already hidden in the lump. Potentiality means a capacity to become something or to do something, and actuality is that capacity realized. A craftsperson who can build and a craftsperson who is building illustrate the distinction. [2]

This lets us describe change without saying that something emerges from sheer nothing: material capable of becoming a cup acquires that form. Naming the capacity still leaves work to do, though. What brings it into action, and what might prevent it? A possibility is not a promise.

A plant does not draw up plans

Now consider a growing plant. Aristotle says that its roots go downward for nourishment. The nourishment enters his explanation as an end: it helps explain the growth by relating it to the plant’s life. He does not need to suppose that the roots imagine a meal and choose a route. Explanation through an end, or through what something is for, is called teleology. [1]

A plant also differs from the cup. Its growth has a source within the living thing, whereas clay has no tendency of its own to form drinking vessels; the potter supplies that direction. This is Aristotle’s more specific sense of nature: an internal source of characteristic change and rest. Having such a source does not make a plant independent of its surroundings. [1]

The final cause is therefore not simply a conscious intention. Nor is it whatever happens last: if the plant withers, the withering does not automatically become the end its growth served. Aristotle allows that natural processes can be obstructed and fail to reach their characteristic outcome.

Why invoke an end?

Aristotle considers an objection. Perhaps useful features arise through material processes and their usefulness is a coincidence, so why add an end to the explanation? He replies that the regular fit between living structures and what sustains life calls for an account. Coincidence, he argues, cannot explain why that fit keeps recurring, and an end can. [1]

Andrea Falcon reads this as a defense of ends as the best explanation of that regularity, not an independent proof that nature contains them. We can feel the force of the question while still asking whether Aristotle has ruled out other explanations, because describing a result as useful does not, by itself, establish why it occurs. [3]

Nor do ends dispense with materials. Our cup cannot hold a drink unless its material and construction allow it, yet a heap of suitable clay will not become a cup by itself. Aristotle’s account asks us to explain how the material requirements belong to the outcome we are explaining, and calling something a purpose cannot do that work for us. [1]

Try the questions

Someone says, “The cup exists because the potter made it. Nothing more needs explaining.” What does that answer cover, and what does it leave open? Then explain why saying that roots grow for nourishment need not attribute a decision to the plant.

Read a possible response

The answer covers only the source of change: the potter’s skilled activity. We can still ask what the cup is made from, what makes that material a cup and what the making is for, and those questions need connected answers, not merely four labels. In Aristotle’s account, nourishment helps explain root growth through its role in the plant’s life; the plant need not foresee that role. This states his proposal without proving it. We must still ask whether the proposed end explains the process and how the necessary material changes occur.

Carry this forward

Before accepting an explanation, ask which question it answers and what it leaves unexplained. An account of an end also invites a further question: is that end worth pursuing? In What would a flourishing life require?, we turn to Aristotle’s account of living well: how habits, judgment and relationships shape a life, and whose opportunities that account leaves unequal.

Sources and limits

[1] Aristotle, Physics, translated by S. Marc Cohen, in Readings in Ancient Greek Philosophy: From Thales to Aristotle, edited by S. Marc Cohen, Patricia Curd and C. D. C. Reeve, fifth edition, Hackett, 2016; ebook ISBN 9781624665943, for the four causes, nature and natural ends. The following were read:

• Book II: chapters 1–3, pp. 481–485, and chapters 7–9, pp. 488–492.
• Editorial material: the work’s editorial introduction; notes 12–15 and 18–19; and the corresponding textual notes at 193b11, 194a29–30 and 194b2.
• Biographical context: selected opening paragraphs of the Aristotle introduction.

The key passages are 192b8–193b21 on nature and form; 194b16–195b30 on causes; 198b10–199b33 on natural ends, including the roots at 199a24–30 and the rejection of a deliberation requirement at 199b26–33; and 199b34–200b9 on material necessity. These are Bekker locators: page, column letter and line in the standard reference edition, which let readers find passages across translations. The anthology warns that its embedded line markers are approximate within the English wording; numbered braces identify print pages. Its credits identify Cohen’s translation copyright 2016.

[2] Aristotle, Metaphysics, translated by C. D. C. Reeve, in the same anthology, for substance, form as explanatory cause, and potentiality and actuality. The following were read:

• Substance and form: Book VII, chapters 1–3, pp. 552–554, and VII.17, pp. 566–567.
• Potentiality and actuality: IX.6, pp. 569–570.
• Editorial material: the work’s editorial introduction, notes 17–18 and the textual notes at 1041b7, 1041b21 and 1041b29.

Reeve often uses “activity” where this lesson uses “actuality.” The anthology credits Reeve’s 2016 translation. Note 18 records that a paragraph from VII.4 has been moved into the anthology’s presentation of VII.3. At 1041b7, the textual note explains that some editions bracket for omission the wording that identifies the cause as form. These editorial choices were checked through the anthology’s notes, without comparing Greek manuscripts. Neither whole treatise, nor the anthology, nor the underlying complete Reeve volume was read, and the gaps between selections remain reading limits.

[3] Andrea Falcon, “Aristotle on Causality”, Stanford Encyclopedia of Philosophy, revised 7 March 2023, §§2–4, for relevant causes, the relation between form and end, and the defense of natural ends. Falcon’s reconstruction is an attributed interpretation and does not settle the philosophical dispute. The complete entry and the works in its bibliography were not read.

The developed cup example, the questions and the response are original teaching material; the root example adapts Aristotle’s own discussion. One identified translation of each primary work was used, without Greek collation, a second translation, independent specialist or learner review, or learner timing. The lesson does not present a complete metaphysical system or a verdict on every modern use of function or purpose.