The Missing Link in Hume's Account of Causal Reasoning
and Causal Belief
Book 1, Part 3:
Section 14. The Idea of
Necessary Connection
Para. 5: What is the
source of the idea of necessity? Not
reason.
Paras. 6-11: The many futile attempts by other
philosophers to solve the puzzle.
Here Hume especially
criticizes the occasionalists (represented by
Malebranche), as explained by Bell in his article in the Cambridge Companion.
The Paradox of Non-Existent Ideas
(Recall Hume’s discussion of substance)
How can Hume claim that we do not have the idea of X without
using that very idea?
Let X = power
“If we have an idea of power, we may attribute power to an
unknown quality. But as ‘tis impossible,
that that idea can be deriv’d from such a quality,
and as there is nothing in known qualities, which can produce it; it follows
that we deceive ourselves, when we imagine we are possest
of any idea of this kind, after the manner we commonly understand
it.”[T1.3.14.11]
What does “after the manner
we commonly understand it” mean? If we
can’t have the idea of power as a hidden quality of objects, how could we
commonly understand it that way?
“We never have any impression, that
contains any power or efficacy. We never
therefore have any idea of power.” [T1.3.14.11]
How can he tell us what idea we don’t have?
Para. 12: Can we get
the idea of cause from the example of our will?
Hume says that we do not perceive the causal power of the
will. He just asserts that we come to
believe in the will’s causal powers by the same process that we acquire any
beliefs about causes.
Could
this be correct? Did you come to believe
in the causal powers of your will by noticing a constant conjunction between
decisions to do X and the corresponding actions? Could you have?
Para. 13: Here Hume
makes an assumption that is not warranted.
He assumes that the only alternative to his account of necessity is the necessity
of demonstration.
Paras. 15-21: A
recapitulation of the account of causal inference. Here Hume’s goal is to convince us that the
only idea of cause is the one that he is able to explain.
Para. 27: What does
Hume mean that he is prepared to allow qualities in material and immaterial
objects with which we are utterly unacquainted?
How could we have an idea of any such properties?
Para. 29: Hume applies his theory of cause to his
causal theory of the mind. Hume’s own
theory of the relation between impressions of sense and ideas is the result of
constant conjunctions in the past.
Para. 31.
Hume's position restated.
The Two Definitions of “Cause”
Para. 31: The
philosophical relation: Cause = “An
object precedent and contiguous to another, and where all the objects
resembling the former are plac’d in like relations of
precedency and contiguity to those objects, that
resemble the latter.”[T 1.3.14.31]
The natural relation:
“A Cause is an object precedent and contiguous to another, and so united
with it, that the idea of the one determines the mind to form the idea of the
other, and the impression of the one to form a more lively idea of the
other.”[T1.3.14.31]
Para. 32: One kind
of cause: All causes are efficient
causes.
Para. 36: Hume’s
parting maxim: “We can never have any reason to believe that any object exists,
of which we cannot form an idea.”[T1.3.14.36]
Section 15. Normative
Hume's Rules to Judge of Causes and Effects [Rules for good causal reasoning,
with a small ‘r’]
1. Contiguity in space and
time
2. Temporal priority.
3. Constant conjunction.
4. Same cause, same effect.
5. Like effects imply(?)
like causes.
Is this true?
6. Different effects must be due to differences
in causes.
7. In some cases, but not all, increases and
diminutions in causes produce corresponding increases and diminutions in
effects.
8. A time separation between a purported cause
and an effect shows that the first is not the sole cause of the effect. [This is a corollary of #1.]
Question: If the mind works by causal laws, how can
there be any norms for good causal reasoning?
Hume’s answer: The mind’s reflection on itself can change
the force and vivacity of its ideas. If
we notice ideas that violate the rules, this very noticing will diminish their
force and vivacity.
Sect. 16: On the reason of animals
What kind of reasoning do
beasts exhibit? Do they need the faculty
of Reason to do it?
Do beasts have
knowledge? Do they have probable belief?
What does Hume mean by
"instinct of animals"? How
does animal instinct confirm Hume's view that belief in cause and effects does
not involve Reason?
What does Hume mean when he
says “reason is nothing but a wonderful and unintelligible instinct in our
souls”[T1.3.16.9]?
Does he mean Reason with a capital “R”?
Puzzles for Hume’s Account of Causal Inference
(1) Pavolovian
conditioning and common causes.
Why don’t we infer that the
sound of a gunshot causes death?
(2) Causes and effects
experienced simultaneously (e.g. a pin prick).
(3) Countervailing
causes: two balanced teams in a tug of
war.
On Hume’s account, doesn’t
this possibility show that nothing is truly a cause. (See T 1.3.15.8)
(4) Hidden causes.
What about things that can
only be known by their effects (e.g. earthquakes)? [Think of Hume’s account of substances.]
What about
hidden mental causes (e.g., memory that is not conscious or the rule that
accompanies an abstract object idea or habit). Have you ever
experienced an unconscious memory or an abstract idea rule or a habit?
Hume's Skepticism About
Bodies (Physical Objects)
A. The Ideas of Existence and External Existence
Book 1, Part 2, Section 6:
There is no idea of existence
separate from our ideas of things (as existing).
Question: How can we have the idea of something (e.g.,
a unicorn) that does not exist?
Key: Can we have the idea of external existence
(of something existing outside the mind)?
Another example of the Paradox of Non-Existent Ideas.
Book 1, Part 4:
Section 1: Skepticism with Regard to Reason
Reason is a kind of
cause. What is the natural effect?
Hume argues that we must
adjust our confidence in the results of our reason based on our past experience
of error. For example, in doing a
complex math problem, we must adjust our confidence in the conclusion based on
the frequency of mistakes we have made in the past on similar problems. How can we estimate the frequency of mistakes
in the past?
This argument is a landmark
in epistemology. It marks the beginning
of the end of pure a priori justification.
Hume then gives a fallacious
argument for why all probability (belief) must eventually degenerate into
improbability (unbelief), and thus why Reason cannot avoid skepticism. We will set that argument aside.
Having disposed of Reason,
Hume is ready to turn his attention to what most interests him, probable belief
based on perception, memory, and the imagination.
Section 2: Skepticism with Regard to the Senses
In this long section, Hume is
going to follow out the implications of his causal theory of the mind.
para. 1: “We may well ask, What causes induce us to believe in the existence of body? But ‘tis in
vain to ask, Whether there be body or not? That is a point, which we must take for
granted in all our reasonings.”[T1.4.2.1]
[See, also, para. 38]
This entire section is not to
convince us to stop believing in bodies, which would be vain, but to clarify
why it is that we believe in bodies.
para. 2: What does Hume mean by "body"?
the concept of body can be divided in two parts: (a) continued existence and (b) distinct
existence. Distinct existence itself has
two parts: (i)
external and (b) independent.
The puzzle: Earlier, Hume had argued that we cannot have
an idea of external existence. How can
we have an idea of continued existence or distinct existence?
The three possible causes of
our belief in body:
paras. 4-13: It's not the senses.
(1) We could not get the idea
of continued existence from the senses.
(2) What about external
existence?
Hume’s
example of the paper beyond his hand, with the fields beyond (para. 9).
Note that here he appeals to
other philosophers for authority, because common sense
would say that we do perceive objects as external to us.
What about independence?
In paras. 12-13,
Hume uses the example of secondary qualities (e.g., color) as a model for all
sensory properties. He takes it for
granted that physics has shown that objects are not colored, but that the
colors are in our minds. He generalizes
that argument to all sensory properties.
para. 14: It's not Reason. Why not?
Even children and peasants
believe in bodies. Their beliefs could
not be based on Reason.
The main argument is that
beliefs about bodies are probable, so they could not be the result of Reason.
paras. 15 ff. It is the
imagination.
How does the imagination give
us the idea of continued and distinct existence? [This is a deep question.]
It cannot be explained by
force and vivacity. Why not?
Paras. 18 and 19: The answer: constancy and coherency.
What is constancy?
What is coherence?
In his explanation, Hume
reverses the order:
paras. 20-22: What is responsible for our belief in
distinct existence? Coherence.
The example
of Hume and the porter.
The example
of the letter.
Note that Hume here seems to
be introducing a new kind of causal inference, not based on constant
conjunction (para. 21). See also paras. 42-44 and 47.
Hume acknowledges that it is
a new kind of inference. Why can’t it be
subsumed by his account of causal inference?
The tension is becoming
intense: How could the imagination infer
an idea (body) that is not derived
from an impression or made up of ideas that are derived from impressions?
paras. 23-24: What is responsible for our belief in
continued existence? Constancy.
On Hume’s account, we produce
the illusion of an idea that continues when it is unperceived. How could we ever form that idea?
Pay attention to what Hume
calls “illusion” or “fiction”.
In para. 29, time
is called a “fiction of the imagination”.
Hume’s
experiment of shutting his eyes (para. 35).
Para. 39: Hume’s
theory of the mind as a “heap or collection of different perceptions, united
together by certain relations”.
Para. 41: What is
the source of the belief in continued
and distinct existence?
Paras. 42-44: Propensity to feign continued existence
bestows vivacity on the “fictions”.
How do we know it is a
fiction?
Para. 45: Hume’s
famous experiment of double perception.
This experiment refutes the
vulgar view of bodies. (What is the
vulgar view?)
Para. 46: What is
the philosophical view? The opinion of double existence.
Paras. 47-48: The philosophical view could not be endorsed
by Reason or the imagination.
Why not the imagination? There is no causal inference from perceptions
to bodies. [In para.
51 Hume attributes the belief to the imagination. Also, recall Hume’s discussion of coherence
in paras. 20-22.]
What is Hume's conclusion?
Why can no one believe it?
But if we could never have an
idea of "body", how could we believe in bodies?
Para. 51: the
difference between reflection and instinct.
Does he think that his
philosophy will stop us from believing in bodies?
How could we ever start believing in something of which we
can have no idea?
Paras. 56-57: Hume began the Treatise as a vindication of
common sense. The final tension is that
now he finds that on reflection, he cannot endorse common sense.
Hume refers to constancy and
coherence as “trivial qualities of the fancy” (para.
56). But it is more plausible to think
that what he has really shown is that they are a powerful kind of reason for
believing in bodies, thought of as “constructs” rather than “fictions”.
Digression on how Quine repeated Hume’s mistake. Both recognized the importance of coherence
relations in reasoning, but did not have any way of explaining how such
reasoning could be possible, because of their simplistic causal theories
(Hume’s reduction of thought to customary connections between perception makes reasoning a kind of conditioning
process. Quine
adopted a more extreme conditioning theory, behaviorism, which replaced
perceptions with patterns of stimulation of our sensory receptors.
Key claim: “’tis impossible for us distinctly to
conceive, objects in their nature any thing but
exactly the same with perceptions.”[T 1.4.2.56]
Why is it impossible?
What is the remedy to these
skeptical doubts? “Carelessness
and inattention” (para. 57). [Instinct? What is
that? It is the laws of the mind,
especially the laws governing the imagination.]