'There are no ideas, which occur in metaphysics, more obscure and
uncertain, than those of power, force, energy or necessary connexion, of which
it is every moment necessary for us to treat in all our disquisitions. We
shall, therefore, endeavour, in this section, to fix, if possible, the precise
meaning of these terms, and thereby remove some part of that obscurity, which
is so much complained of in this species of philosophy.' Hume, Enquiry,
Section VII Part 1.
'When we look about us towards external objects, and consider the
operation of causes, we are never able, in a single instance, to discover any
power or necessary connexion; any quality, which binds the effect to the cause,
and renders the one an infallible consequence of the other. We only find, that
the one does actually, in act, follow the other. The impulse of one
billiard-ball is attended with motion in the second. This is the whole that
appears to the outward senses. The mind feels no entiment or inward impression
from this succession of objects: consequently, there is not, in any single,
particular instance of cause and effect, any thing which can suggest the idea
of power or necessary connexion.' Hume, Enquiry, Section VII Part
Let me outline the view I have
been trying to present of Hume's thoughts on causality. (There is plenty of
room for other interpretations, I'm afraid).
He says
1. Before philosophizing, we think of causality as a
applying when one event happens and brings another about.
2. When you observe one event 'causing' another you never
perceive any 'necessary connection' linking the two.
3. This means you don't derive the idea of 'necessary
connection' from sense.
(4. You don't get it either from introspection.)
5. So on empiricist principles, there is no idea of
'necessary connection'.
6. What generates then the illusion that we have such an
idea?
We form a mental habit on the
basis of constant conjunctions and project this onto the world.
One of the key steps in Hume's
argument is to say that we can have no real idea of necessary connection,
because when we perceive a putatively causal relationship we do not perceive
any necessary connection (or actual 'link').
This step is key, because on
empricist principles, if the idea of necessary connnection doesn't come from
experience, it can't be meaningful.
'It seems a proposition, which will not admit of much dispute,
that all our ideas are nothing but copies of our impressions, or, in other
words, that it is impossible for us to think of anything, which we have not
antecedently felt, either by our external or internal senses.' Hume, Enquiry,
Section VII Part 1.
Might introspection on the
operation of our will be the source of our idea of necessary connection?
Hume addresses this suggestion:
'Since, therefore, external objects as they appear to the senses,
give us no idea of power or necessary connexion, by their operation in
particular instances, let us see, whether this idea be derived from reflection
on the operations of our own minds, and be copied from any internal impression.
It may be said, that we are every moment conscious of internal power; while we
feel, that, by the simple command of our will, we can move the organs of our
body, or direct the faculties of our mind. An act of volition produces motion
in our limbs, or raises a new idea in our imagination. This influence of the
will we know by consciousness. Hence we acquire the idea of power or energy;
and are certain, that we ourselves and all other intelligent beings are
possessed of power. This idea, then, is an idea of reflection, since it arises
from reflecting on the operations of our own mind, and on the command which is
exercised by will, both over the organs of the body and faculties of the soul.'
Hume, Enquiry, Section VII Part 1.
First Hume considers the
suggestion that it is our awareness of our voluntary control over our body that
gives us the idea of necessary connection. His objection: you can't predict what will happen following the
act of will. Three reasons why prediction from an act of will is impossible
First, we don't understand how
the will acts on the body.
'[If] by consciousness we perceived any power or energy in the
will, we must know ... its connexion with the effect; we must know the secret
union of soul and body ...' Hume, Enquiry, Section VII Part 1
Second, we can affect some
things with the will but not others (eg, as Hume thought, our heartbeat). But
we don't understand why. Hume says that if we truly had the idea of necessary
connection as linked on the one hand to the will, we should understand
why:
'Secondly ... Why has the will an influence over the tongue and
fingers, not over the heart or liver? This question would never embarrass us,
were we conscious of a power in the former case, not in the latter. We should
then perceive, independent of experience, why the authority of will over the
organs of the body is ircumscribed within such particular limits. Being in that
case fully acquainted with the power or force, by which it operates, we should
also know, why its influence reaches precisely to such boundaries, and no
farther.' Hume, Enquiry, Section VII Part 1.
Under the second heading, Hume
also invites us to consider the case of paralysis:
'A man, suddenly struck with palsy in the leg or arm, or who had
newly lost those members, frequently endeavours, at first to move them, and
employ them, in their usual offices. Here he is as much conscious of power to
command such limbs, as a man in perfect health is conscious of power to actuate
any member which remains in its natural state and condition. But consciousness
never deceives. Consequently, neither in the one case nor in the other, are we
ever conscious of any power. We learn the influence of our will from experience
alone. And experience only teaches us, how one event constantly follows
another; without instructing us in the secret connexion, which binds them
together, and renders them inseparable.' Hume, Enquiry, Section VII Part
1.
Hume's third argument is that
what we actually succeed in doing, when we will something, according to
anatomy, is to bring about changes in the nervous system. These changes by a
chain of events eventually results in the acion we will. This shows we cannot
be aware of any power in the will, because if we did we would know what event
the volition would bring in its train, and we don't (we rely on anatomy to tell
us):
'Thirdly, we learn from anatomy, that the immediate object of
power in voluntary motion, is not the member itself which is moved, but certain
muscles, and nerves, and animal spirits, and, perhaps, something still more
minute and more unknown, through which the motion is successively propagated,
ere it reach the member itself whose motion is the immediate object of
volition. Can there be a more certain proof, that the power, by which this
whole operation is performed, so far from being directly and fully known by an
inward sentiment or consciousness is, to the last degree, mysterious and
unintelligible? Here the mind wills a certain event. Immediately another event,
unknown to ourselves, and totally different from the one intended, is produced:
This event produces another, equally unknown: till at last, through a long
succession, the desired event is produced. But if the original power were felt,
it must be known: were it known, its effect also must be known; since all power
is relative to its effect. And vice versa, if the effect be not known, the
power cannot be known nor felt.' Hume, Enquiry, Section VII Part 1.
'We may, therefore, conclude from the whole, I hope, without any
temerity, though with assurance; that our idea of power is not copied from any
sentiment or consciousness of power within ourselves, when we give rise to
animal motion, or apply our limbs to their proper use and office. That their
motion follows the command of the will is a matter of common experience, like
other natural events: But the power or energy by which this is effected, like
that in other natural events, is unknown and inconceivable.' Hume, Enquiry,
Section VII Part 1
Do we get gthe idea of
'necessary connection' from acts
of will in creation?
'Shall we then assert, that we are conscious of a power or energy
in our own minds, when, by an act or command of our will, we raise up a new
idea ... ?'
His answer is that this won't
work either.