David Hume on Causality
What impression corresponds to the idea of causality? Answer: None
Causality. Commonsense view: A necessarily causes B to happen
Hume: A and B are quite distinct. There is no necessary connection.
Cause and effect. We might think initially that this can be analysed as involving constant
conjunction. But things are always coming together without one causing the other. Winter
weather does not itself endanger the lives of turkeys – it just so happens that Christmas falls
in winter, and this is when turkeys are liable to be killed. There is constant conjunction
between winter and turkey deaths but winter itself does not cause the deaths.
So what other factors does Hume consider?
(1) Contiguity in space and time (the same principle in the association of ideas)
(2) Priority of cause
(3) Necessary connection
Problem with contiguity: action at a distance, such as gravity. We do not get impression of
contiguity every time events are linked by cause and effect. for example we see hot sun and
melted butter. But there is contiguity of the heat and of the melted butter?
Problem with priority
We do not see the contact of the first with the second billiard ball to be slightly earlier than
the second ball starting to move; but this is perhaps merely a limitation of our eyes.
But even if we did get impressions of contiguity and priority these would not be enough
to explain casualty. Two things can be related in these ways purely by chance. I might look
at a clock just as it starts to chime – so contiguity and priority are present – but my looking
does not cause the clock to chime.
Causality involves the belief that effect B happened because of event A. That given A, B
had to happen
BUT we have no impression of this NECESSARY CONNECTION. We do not perceive
the necessity. But we have the idea, which does not come from an impression. This runs
against Hume's claim that all ideas arise as a result of earlier impressions. So where does it
come from?
What role does custom and habit play in Hume’s argument?
Kant: our minds are structured so that we could not operate unless we had the belief that
every event has a cause. We would not understand what it is for something to happen unless
we believed that it was caused.
But Hume does not believe this. Experience does not tell us, and it is not contradictory to
deny that every event has a cause (it is not analytically true that EC). His reasoning is that
the ideas of cause and effect are wholly distinct from one another. We can conceive
something suddenly coming into existence uncaused, of an event without a cause. So we
cannot conclusively demonstrate that very event had a cause.
Why do we then believe that it has? The idea of necessary connection involves habits and
dispositions of the mind.
Problem: I am not certain whether it is true that the ideas of cause and effect are distinct
from each other. Surely we might in principle imagine something being uncaused, BUT can
only define causes and effect in terms of each other? Because we can imagine something
being the case does not establish that Hume is correct. We can imagine all kinds of
impossible things. I believe that either (1) Kant is correct and that our mind is structured so
that it makes sense of the world only because we always assume EC Assuming the truth of
EC is a precondition of experience) or (2) that EC is analytic.
General problem: Hume needs the principle of causality in theory of ideas.
The problem is that there need be no impression of necessary connection. If we observe 2
events, we see only one event followed by another. We don’t perceive the necessity. If 2
billiard balls hit each other, we see one ball hitting another and the second moving away.
If there is no impression there is no idea.
Hume concludes there is no such thing as necessary connection.
The point here is that causality involves far more than Constant Conjunction: that is, one
thing always following another. We want to say that if A happens then B necessarily
happens.
The necessary connection itself is never observed no matter how many times we make the
observation. You can watch these boxes hitting each other for the rest of your life and all
you’ll see is one hitting the other and the other moving away. Also, like causes give rise to
like effects.
How then do we get the idea of necessary connection?
Hume’s answer is that our mind gets in to the habit of expecting to see the effect whenever it
sees the cause. It is something we just do, there is no ultimate justification for it.
A HABIT OF MIND generates the connection. The mind works in such a way as to
bring about the idea of necessary connection.
Every effect has a cause: according to Kant, a synthetic a priori proposition. A necessary
truth but not merely a matter of how we define ‘cause’ and ‘effect’. Framework imposed on
the world by the way our minds work.
Hume is thus sceptical about the rationality of our belief in causation.
