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Unit 5: Core Concepts in Metaphysics
Concept of Substance
Substance is one of the most central and disputed concepts in metaphysics. It refers to the "ultimate stuff" of reality, the fundamental "thing" that "stands under" (sub-stare) and supports all of an object's properties.
Substance is traditionally defined as that which can exist *independently* on its own, and which persists through change. It is the "owner" of properties (qualities, attributes).
Example: An Apple
- We perceive its *properties*: "red," "round," "sweet," "hard."
- But what is the "it" that *has* these properties? We call this "it" the substance.
- The properties can change (the apple can become "brown" and "soft"), but we still assume the underlying "substance" (the apple itself) remains the same.
Philosophical Views on Substance:
| Philosopher |
View on Substance |
| Aristotle |
A concrete, individual thing (e.g., "this man" or "this horse"), a composite of Form and Matter. |
| Descartes (Rationalist) |
There are three substances: God (the only true, independent substance), Mind (whose essence is thinking), and Matter (whose essence is extension/size). |
| Spinoza (Rationalist) |
There is only one infinite substance, which he called "God" or "Nature." Mind and matter are just two "attributes" of this one substance. |
| Locke (Empiricist) |
We must *assume* a substance exists as an "I know not what" (a "substratum") to support the qualities we perceive, but we can never *experience* it directly. |
| Hume (Empiricist) |
Rejects substance. Since all knowledge is from experience, and we only ever experience a "bundle" of properties (red, sweet, round), we have no basis for believing in an *extra* "thing" called substance. "Substance" is just a word we use for this bundle. |
Concept of Space
What is space? Is it a "thing" in itself, or just a "relationship" between things?
- Absolute View (Newton): Space is like a giant, invisible, empty "container" or "stage." It is absolute, real, and exists independently of any objects in it. Objects are *in* space, and space would still exist even if all objects were removed.
- Relational View (Leibniz): Space is *not* a "thing." It is merely a *set of relations* between objects. "Space" is just a way of describing distances and directions (e.g., "to the left of," "five feet from"). If there were no objects, there would be no relations, and thus no "space."
- Kantian View (Kant): Space is neither a thing nor a relation "out there." It is a fundamental "form of intuition"—an "inner goggle" of the human mind. We are "hard-wired" to perceive all *external* objects as existing *in* space.
Concept of Time
What is time? This concept is deeply linked to the concept of space.
- Absolute View (Newton): Time is like a giant, invisible "river" that "flows" at a constant rate, everywhere in the universe. It is absolute, real, and exists independently of any events that happen *in* it.
- Relational View (Leibniz): Time is *not* a "thing." It is merely a *set of relations* between events. "Time" is just a way of describing the order of events (e.g., "before," "after," "simultaneously"). If nothing ever changed or happened, there would be no "time."
- Kantian View (Kant): Time is the *other* "form of intuition." It is the "inner goggle" through which we experience all *internal* states (our thoughts, feelings) and *also* order all external events.
Exam Tip: Remember Kant's pairing.
- Space = The mind's form for all outer sense.
- Time = The mind's form for all inner sense (and by extension, all sense).
Concept of Causality (Hume)
This is one of the most famous and important arguments in modern philosophy. The syllabus specifically points to David Hume, the radical empiricist.
The Question: What is causality (cause and effect)? When we say "A causes B" (e.g., "The cue ball hitting the 8-ball *causes* it to move"), what do we actually *know*?
Before Hume, philosophers (like Rationalists) believed that causality was a "necessary connection." They thought there was a real, logical, and necessary "force" or "power" in the cause (A) that *made* the effect (B) happen.
Hume's Critique of Causality
Hume, as a strict empiricist, applies his test: "If all knowledge comes from experience (impressions), show me the *impression* of causality."
Hume's Analysis:
When we observe a "causal" event (like one billiard ball hitting another), what do we *actually* see?
- Contiguity (in Space and Time): We see event A (the first ball moving) and event B (the second ball moving) happen next to each other, in an unbroken sequence.
- Priority (in Time): We see event A happen *before* event B.
- Constant Conjunction: We have seen this *same sequence* happen over and over again in our past (e.g., every time one ball hits another, the second one moves).
The "Missing" Ingredient:
Hume points out that no matter how hard we look, we *never* perceive the "cause" itself.
"We never have an impression of a 'necessary connection,' a 'power,' or a 'force' passing from ball A to ball B. We only see a *sequence* of events. We see A, *then* B."
Conclusion: Since we have no *impression* of a "necessary connection," we have no *knowledge* of a "necessary connection." The idea that causes *force* or *compel* their effects is a fiction. We cannot prove, either by reason or by experience, that any two events are necessarily linked.
Hume's Solution: Causality as Psychological Habit
So, if causality isn't "in the world," why do we believe in it so strongly? Hume gives a psychological explanation.
Our belief in causality is not based on *reason* or *perception*, but on psychological habit (or "custom").
- After observing the "constant conjunction" of A and B thousands of times, our mind develops a "habit of association."
- When we see A happen again, our mind *automatically* and *instinctively* *expects* B to happen.
- We then (falsely) project this *internal feeling of expectation* onto the external world, and call it a "necessary connection."
Final Summary of Hume's View:
- What causality *is* in the world: Just a "constant conjunction" of events.
- What we *think* causality is: A "necessary connection."
- Where this idea comes from: A "psychological habit" formed by observing this conjunction.
Exam Tip: Hume's critique of causality is a powerful example of empiricist skepticism.
- He does not deny that there is a *regularity* in the world (e.g., the sun will "probably" rise tomorrow).
- He *does* deny that we can be *rationally certain* that this regularity is "necessary" or that the sun *must* rise.
- This is the argument that "awakened" Kant and led him to develop his Critical Theory (Unit 3) to "save" causality by placing it *in the mind*.
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