Aristotle's Types of Change

Hello! Welcome back to our course on Aristotle's theory of the immovable mover.

Introduction

In our last session, we grappled with the core definition of change, or kinēsis, concluding that it is the actuality of a potentiality, as such. This definition captures the essence of change as an ongoing, incomplete process—the state of being on the way from a potential state to an actual one.

Having established what change is in general, our task now is to categorize its different kinds. This is not just a matter of classification; distinguishing between the types of change is crucial for understanding the specific causal principles Aristotle applies to them, which in turn form the building blocks of his argument for a First Mover.

Today's learning outcome is to distinguish between the different types of change in Aristotle's physics: generation/corruption, alteration, and locomotion. We will see how these different types of change relate to Aristotle's categories of being and differ in how fundamentally they affect a substance.

1. The Four Domains of Change

In the previous lesson, you saw a brief overview of four kinds of change. Aristotle formally derives these by arguing that genuine change can only occur in four of his categories of being. Let's start by reading the definitive account of this from the Stanford Encyclopedia of Philosophy.

As you've just read, Aristotle identifies four fundamental domains where change happens:

1. Substance (Ousia): Change regarding what a thing is.
2. Quality (Poion): Change regarding a thing's properties or attributes.
3. Quantity (Poson): Change regarding a thing's size or amount.
4. Place (Topos): Change regarding a thing's location.

These four domains give rise to the main types of change we will now examine in detail. A key point to note is the distinction Aristotle often makes: he sometimes uses "motion" (kinēsis) in a stricter sense to refer only to changes in quality, quantity, and place, while setting aside change in substance as a more radical transformation.

2. A Taxonomy of Change

Let's now explore each type of change, linking it back to its corresponding category.

A. Generation and Corruption (Change in Substance)

This is the most fundamental type of change. It is not merely a modification of an existing subject, but the coming into being of a new substance or the passing away of an old one.

To understand this, let's look at the text that is literally named for this process, On Generation and Corruption.

As the article states, generation and corruption are opposites:

• Generation (Genesis): A substance coming into being (e.g., an acorn, through a long process, ceases to be an acorn and becomes an oak tree).
• Corruption (Phthora): A substance passing away (e.g., a log burns and ceases to be wood, becoming ash and smoke).

In these cases, the original substance does not persist. The change is in the substantial form itself. While some underlying matter must persist (a topic Aristotle explores with the concept of prime matter), the thing, as the kind of thing it was, is gone.

B. Alteration (Change in Quality)

Alteration is a change in the qualities of a substance that otherwise remains the same.

• Alteration (Alloiosis): A change in an accidental quality of a substance.
  • Example: A leaf changing color from green to yellow. It is still the same leaf (substance), but its quality (color) has changed. Other examples include a person becoming educated, water becoming hot, or a piece of iron rusting.

The key distinction is that the substance persists through the change. The leaf is still a leaf; the water is still water. The change is not to its essence but to one of its non-essential properties.

C. Locomotion (Change in Place)

This is the type of change that most closely corresponds to our modern, everyday use of the word "motion."

• Locomotion (Phora): A change in the location of a substance.
  • Example: A ball rolling across the ground, a planet moving through the heavens, or you walking from one room to another.

Of all the types of change, locomotion is the least transformative. It does not affect the intrinsic being of the object at all. The SEP article you read earlier makes this point well: "locomotion, as Aristotle claims, affects the least the substance... of the object undergoing motion" (from resource 1ff42). A change of place is purely extrinsic; the object itself remains identical in its substance, qualities, and quantity.

D. Increase and Diminution (Change in Quantity)

This final category concerns changes in size or amount.

• Increase (Auxēsis) and Diminution (Phthisis): A change in the quantity of a substance.
  • Example: A puppy growing into a large dog, or a person losing weight.

Like alteration, the substance persists through the change. The puppy is the same substantial being as the adult dog, but its quantity has changed.

3. Synthesis and Summary

We have now identified the main types of change and their corresponding categories. To bring it all together, let's watch the full, short video from Gregory Sadler, which presents a consolidated overview.

To formalize these distinctions, here is a summary table. This structure should resonate with the way you might classify different types of transformations or functions in a formal system.

Type of Change	Category of Being	What Changes?	Example	Does the Substance Persist?
Generation/Corruption	Substance	The Substantial Form itself	An acorn becomes an oak tree	No (a new substance is formed)
Alteration	Quality	An Accidental Quality	Water becomes hot	Yes
Increase/Diminution	Quantity	An Accidental Quantity	A child grows taller	Yes
Locomotion	Place	The External Relation to place	A ball rolls across the floor	Yes

This classification is not merely academic. The distinction, especially between substantial change and locomotion, becomes critical. The argument for an Unmoved Mover in the Physics is primarily an argument to explain the eternal locomotion of the celestial spheres, whereas the argument in the Metaphysics is a broader argument to explain the existence of change and being as such.

Conclusion

In this lesson, we have systematically categorized the different types of change according to Aristotle's physics.

Key Takeaways:

• Aristotle identifies four primary domains of change, corresponding to the categories of Substance, Quality, Quantity, and Place.
• Generation and Corruption are changes of substance, where a new substance comes to be or an old one passes away. The original substance does not persist.
• Alteration, Increase/Diminution, and Locomotion are "motions" where the substance persists through the change.
  • Alteration is a change in quality.
  • Increase/Diminution is a change in quantity.
  • Locomotion is a change in place and is the most superficial type of change, affecting the substance the least.
• These types of change are irreducible to one another.

Preview of the Next Lesson:

With this taxonomy of change in place, we are now ready to analyze the causal principles that govern them. In the next lesson, we will examine one of the most famous and pivotal premises in Aristotle's entire system: the principle that 'whatever is moved is moved by another'. We will explore what this principle means, why Aristotle believed it was necessary, and how it applies to the different types of change we've just defined.