An Enquiry Concerning Human
Understanding
Philosophy 1
Spring, 2002
G. J. Mattey
British Empiricism
• John Locke (1632-1704) adopted Descartes’s
“new way of ideas”
• Locke rejected innate ideas, claiming that all ideas
come from experience
• He also held that all that can be known on this
basis is our own existence, the existence of God,
and that of material things we are now sensing
• George Berkeley (1695-1753) denied the existence
of matter altogether
David Hume
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Born 1711
Scottish
Historian of England
Popular essayist
Worked in diplomacy
Denied teaching
position due to charges
of atheism
• Died 1776
Hume’s Contributions
• Argued for moderate skepticism in theoretical
matters
– Cause and effect
– Personal identity
– Existence and nature of God
• Tried to base geometry on sensory experience
• Originated the “belief-desire” account of human
action
• Proposed an ethical theory based on the feeling of
sympathy
Species of Philosophy
• There have been two prevailing species of
philosophy
– A popular philosophy, which is easy to
comprehend and which motivates people to act
virtuously
– An abstruse philosophy, which is difficult and
which seeks to understand the principles
governing human nature
Reason and Action
• Profound research is thought to be useless, and it
produces uncertainty that leads to melancholy and
rejection
• It cannot be sustained in a social setting
• Merely acting, while ignorant, is despised
• The mind needs rest from constant activity
• The best life is a mixed one
• “Be a philosopher, but, amid all your philosophy,
be still a man”
Metaphysics
• Metaphysics is accurate and abstract
• Accuracy is advantageous to art, business,
government, law, etc.
• The study of metaphysics is pleasurable to those
with vigorous minds
• But its obscurity harbors error by giving shelter to
superstition
• This is why metaphysics must be pursued, yet in
an “easy” manner
The Powers of the Mind
• An investigation of the powers of the mind will
show it unsuited for the investigation of remote
and abstruse subjects
• It is satisfying in itself to map the powers of the
mind
• Can we discover the fundamental sources of these
powers?
• Since they have not been discovered yet, it must
be hard to find them
The Origin of Ideas
• Impressions are original, lively thoughts
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Sensations
Emotions
Desires
Volitions
• Ideas are less-lively copies of impressions
• All (or nearly all) ideas are copies of impressions
• The test for validity of an abstruse philosophical
idea is to find the impression of which it is a copy
The Association of Ideas
• Ideas and impressions occurring in the mind
are connected by general principles
• Even the most disorganized thought has
some thread of order in it
• There are three such principles
– Resemblance
– Contiguity
– Cause and effect
Relations of Ideas
and Matters of Fact
• Mathematical sciences, which are
intuitively or demonstratively certain,
concern only relations of ideas
• They are based on mere thinking
• Other objects of investigation concern
matters of fact
• There is no contradiction in denying them
• So what evidence do we have of their truth?
Cause and Effect
• The senses and memory attest to the real existence
of things
• This testimony is extended by reasoning about
cause and effect
• This reasoning moves from a present fact to a
remote fact
• It does so through the presumption of a real causal
connection between the facts
• But how is this connection known to hold?
Cause and Effect Discovered
through Experience
• We do not know a priori what effect will
follow from a given cause
• Only experience allows us to discover the
connection, e.g., that bread nourishes
• Custom conceals this reliance on experience
• We cannot without experience predict a
particular effect
• Nor can we discover the general relation
Ultimate Causes Unknown
• The best we should hope for in natural
philosophy is to reduce the causes of natural
phenomena to a few (gravity, cohesion)
• These are based on analogy and observation
• The causes of these causes are beyond our
reach
• Mathematics cannot uncover causes
Causal Reasoning
• Causal reasoning is based on experience
• What justifies our use of experience to draw
conclusion about matters of fact?
• We connect sensible qualities with “secret
powers”: bodies with the perceived qualities of
bread have the power to nourish us
• By what reasoning do we extend the “power”
observed in one piece of bread to an unobserved
piece?
• There is no apparent “medium” to connect the two
The Missing Link
• There can be no demonstration connecting
the observed with the unobserved
• The opposite can always be conceived
• So the connection could only be established
by probable reasoning about matters of fact
• All such reasoning is based on similarity
• What is the medium connecting the similar
to the similar?
Begging the Question
• It might be said that experience is the
required medium
• It could serve as a medium only if the future
resembles the past
• We infer that the future resembles the past
only on the basis of experience
• But this use of experience then requires the
premise that the future resembles the past
Is There an Inference At All?
• We do not know how to support the
inference from the observed to the
unobserved
• It may be that there is no inference at all
• A child learns at once to avoid a hot surface,
and no inference seems to be involved
Skepticism
• Skepticism talks of doubting, suspending
judgment, refraining from rash conclusions
• As such, it does not ally itself with any of the
passions, except love of truth
• For this reason, it is stigmatized as libertine,
profane, and irreligious
• But skepticism about the basis of causal inference
does not undermine ordinary reasoning
Custom and Habit
• The reason we make judgments based on
experience and refrain from then when lacking
experience is custom or habit
• This allows us to conjoin things which in
themselves are dissimilar, such as weight and
solidity
• Custom “is the great guide to human life”
• It always terminates in a present sensation or
memory
Belief
• The difference between belief and fiction is
not to be found in the idea itself
• Instead, it is a feeling found in belief alone
• It gives [ideas] more weight and influence,
makes them appear of greater importance,
enforces them in the mind, and renders
them the governing principle of our action”
Mechanisms of Belief
• Belief is an intense idea of something
• In the case of the relation of cause and effect, the
idea of one thing is intensified in the presence of
the idea of another
• The same holds for resemblance: our idea of a
friend is intensified by a picture of him
• And also for contiguity: my idea of my home is
more intense upon my approach
• Custom accounts for all these phenomena, in
harmony with nature
Probability
• Although there is no chance in the world,
our ignorance of causes makes it seem as if
there is
• Our beliefs about “chances” reflect the
intensity of our ideas of each alternative
• Our ideas of causes vary in intensity with
the number of cases
• If enough cases concur, there is belief
Necessary Connection
• Mathematics deals with clear concepts, but
with complicated inferences
• Metaphysics deals with obscure concepts,
though its inferences are short
• The most obscure ideas in metaphysics are
those of “power, force, energy, or necessary
connection”
• What impression lies behind them?
Sources of the Idea
• Ideas of external objects do not reveal
necessary connections
• We experience only the conjunction; the
power remains hidden
• It is thought that experience of our willing a
change in one’s body reveals a power
• But this pretension will be exploded
Willing to Move
• The consequences of our willing can only
be determined through experience
• We do not know how mind and body are
connected
• We lack control over some parts of our body
• We do not bring about movements directly
Willing Ideas
• It is also thought that will is the power to
produce or control ideas
• But we lack an impression of this power
– We do not know how the mind brings about
ideas
– We lack control over some ideas
– Our control is variable
Occasionalism
• Nicolas Malebranche and others claimed
that only God is a cause, and alleged causes
are only occasions for God’s causality
• This view detracts from God’s power
• It also has philosophical defects
– It too-boldly carries us beyond experience
– We are as ignorant of any causal power in the
mind as in bodies
The Origin of the Idea of Power
• All we discover through experience is
conjunction, not connection
• Do we, then, have no idea of power at all?
• When there is constant conjunction, we assert that
there is a causal connection
• The only similarity in the conjunction is repetition
of similar instances
• We feel a transition, and this feeling is the
impression from which the idea of power is copied
Causality Defined
• A cause can be defined in terms of the
feeling of transition
• One definition of cause is “an object
followed by another and whose appearance
always conveys the thought to that other”
• This transition is explained in terms of
custom and habit
Antecedent Skepticism
• Descartes sought to prevent error and thus doubted
what he could
• By bringing his own faculties under doubt, he
prevented any possibility of removing doubt
• If there were any self-evident starting point for
recovery from doubt, its application would involve
the faculties in question
• A more moderate version is useful: to begin with
what is self-evident and make only small steps
Consequent Skepticism
• Some skeptics focus on the actual
deficiencies in our mental faculties
• Sensory illusion is generally cited
• But it can be corrected through reason
• A more difficult problem lies in the natural
tendency to suppose that the images of the
senses are external, independent objects
Doubting the Senses
• Philosophy shows that the images of the senses are
distinct from independent objects
• At best, they are copies of those objects
• But the claim of resemblance cannot be justified
– We do not know the origin of the images
– And we have no way to compare the two
– Appeal to God is ruled out
• So the teachings of nature are incorrect, and those
of philosophy lead to skepticism
Primary and Secondary Qualities
• It can be shown that the claim of resemblance is
contrary to reason
• We cannot abstract extension from color, primary
from secondary qualities
• Secondary qualities depend on the senses and exist
in the mind
• Primary qualities are no different
• So, primary qualities exist in the mind
• All that is left is an “unknown something”
Skepticism About Mathematics
• Abstract reasoning involving space and time
fall prey to paradoxes of the infinite
• A real line is divided into infinitely many
parts, each one of which is infinitely
divisible
• But this itself is paradoxical, because the
initial ideas seem clear, so we are skeptical
of our skepticism
Pyrrhonism
• Extreme skepticism would have us doubt all
reasoning concerning matters of fact
• But this Pyrrhonism is overcome by our need to
act
• Nothing of any lasting value results from it—it is
mere amusement
• So the skeptic should confine himself to
philosophical objections into abstract matters,
such as causality
Mitigated Skepticism
• Most people are dogmatic, as this is the
most effective way to bring about action
• Some skepticism might cure them of this
• A just reasoner will always entertain some
doubt and caution
• Another form of mitigated skepticism
restricts human investigation to what lies in
experience (not the supernatural, e.g.)