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The Empiricists: David Hume
There is no justification for believing that there is any causal necessity in the ordering of events avid Hume 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 Quine would later famously say, echoing Hume, what can be garnered from the senses is, after all, not much. From 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 demolitionary – 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 A618C90F-C2C6-4FD6-BDDB-9D35FE504CB3
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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, and human belief in causation is 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. 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 generalizations 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.
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