EMPIRICIST & ESSENTIAL THINKER (1711–1776)

– A narrative and critique on the philosophy of David Hume

David Hume is the philosophical hero of modern day sceptics and empiricists, renouncing all knowledge except 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 had drawn 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 experimental psychology in search of general principles. In this, however, Hume can be seen as being spectacularly unsuccessful, 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 problematic for modern philosophers.

Hume observes that we never experience our own self, only the continuous chain of experiences themselves. This psychological fact leads Hume to the dubious metaphysical conclusion that the self is an illusion, and 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 being 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 casual necessity in the ordering of events.

Hume’s scepticism does not stop there, and the 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 justifiably led to 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 pressing for philosophers of science. Trying to show how induction is justified has taxed them throughout the 20th and 21st Centuries. Karl Popper is notable for offering the most promising solution to Humean scepticism. Popper’s brand of scientific method, ‘falsificationism’ gave rise to a whole new area of debate in the philosophy of science. According to Popper, the mark of a scientific theory is whether it makes predictions which could in principle serve to falsify it.