David Hume (1711-1776) is
the philosophical hero of modern day sceptics and empiricists, renouncing all
knowledge except for that which can be gained from the senses. Alas, as W.V.O. Quine
would later famously say, echoing Hume, what can be granted from the senses is,
after all, not much.
From John Locke, Hume drew
the conclusion that all human knowledge is based on relations amongst ideas, or
‘sense impressions.’ Anything not
given in experience is mere invention and must be ruthlessly discarded. As a
result he denies the existence of God, the self, the objective existence of
logical necessity, causation, and even the validity of inductive knowledge
itself. His aim is twofold: at once demolitionnary
– to rid science of all falsehoods based on ‘invention rather than experience’ – and constructive, to found a science of human nature.
Much impressed with how
Isaac Newton had described the physical world according to simple mechanical
laws, Hume had a mind to do something similar for the nature of human
understanding. His Treatise on Human
Nature is a painstaking study in experiential psychology in search of
general principles. In this Hume can be seen as having failed spectacularly,
primarily because his whole taxonomy of ‘impressions’ and ‘ideas’ is derived
from the much discredited Cartesian model. Nevertheless, Hume’s negative
program is a devastating example of the power of logical critique. His sceptical
results, especially regarding induction, remain a problem for modern
philosophers.
Hume observes that we
never experience our own self only the continuous chain of our experiences
themselves. This psychological fact leads Hume to the dubious metaphysical
conclusion that the self is an illusion, and that in fact personal identity is
nothing but the continuous succession of perceptual experience. “I am,” Hume famously says, “nothing but a bundle of perceptions.”
Following a similar line
of thought, Hume notices that the force that compels one event to follow
another, causation, is also never experienced in sense impressions. All that is
given in experience is the regular succession of one kind of event followed by
another. But the supposition that the earlier event, the so-called ‘cause,’ must
be followed by the succeeding event, the ‘effect,’ is merely human expectation
projected onto reality. There is no justification for believing that there is
any causal necessity in the ordering of events.
Hume’s scepticism does not
stop there. He regards human belief in
causation as just a special case of a more general psychological trait:
inductive reasoning. Inductive reasoning is the process that leads us to
make generalisations from observing a number of similar cases (remember
frictional character Sherlock Holmes?). For example, having observed many white
swans but no black swans, one might seemingly be justified in the conclusion
that “All swans are white.” Equally, being aware that men often die, we
conclude “All men are mortal.”
But such generalisations
go beyond what is given in experience and are not logically justified. After all,
black swans were found in Australia, and there is always the logical possibility
of coming across an immortal man.
Hume claimed that
inductive reasoning could not be relied upon to lead us to the truth, for
observing a regularity does not rule out the possibility that next time
something different will occur.
Since all scientific laws
are merely generalisations from inductive reasoning, this so-called ‘problem of
induction’ has been an urgent one for philosophers of science. Trying to show
how induction is justified has taxed them throughout the 20th
century. Karl Popper is notable for offering the most promising solution to
Humean scepticism.
[Summarized from Philosophy 100 Essential Thinkers by
Philip Stokes, 2012.]
Lord, Give
Us Today Our Daily Idea(s)
