David Hume


The Scottish philosopher David Hume is one of the most brilliant and skeptical of philosophers. Our ideas of epistemology would have been very different had Hume not been born. He developed empiricist philosophy to its logical zenith and challenged traditional philosophical beliefs in such drastic a manner that the world was shocked. And his sharpness remains supreme because his arguments have still not been countered effectively. Indeed, such is the nature of Hume’s philosophy that Russell is led to state: “There are only two attitudes towards Hume’s arguments: to accept them, or to ignore them.” So, let us see what this skeptic has to say.

Hume presented his views in his chief philosophical work Treatise of Human Nature, which, against Hume’s expectations, was completely ignored by the philosophers. (In Hume’s own words: it fell dead-born from the press.) Later, Hume shortened and diluted the Treatise into Inquiry into Human Understanding, and it was through this book that he was known. It was after reading the Inquiry that Kant began the journey of his own philosophical thinking.

Hume begins with a distinction between our mental contents: impressions and ideas. Impressions are the direct, clear and forceful result of immediate experience; ideas are the faint and faded copies of these impressions. For example, the words you are reading right now on this page are impressions, but the words of your last assignment present in your memory are ideas. Hume says that every simple idea has a simple impression, and every simple impression has a corresponding idea. This is clearly a restatement of Locke’s principle that all ideas must enter through experience. Therefore, if no impression is associated with a term, it means that the term is altogether insignificant. And Hume uses this technique to analyze many of the terms we use, such as ‘causality’, ‘matter’ and ‘mind’.

Our mind links ideas in many different ways such as resemblance [Adam looks like James], contiguity [you are sitting on the chair] and cause-and-effect [a moving marble striking a stationary marble causes the latter to move].

Hume distinguishes between two sorts of beliefs: Relations of Ideas and Matters of Fact. The former deals with only association of ideas within the mind and includes logic and mathematics. The latter concerns the nature of existing things, and it is these sorts of beliefs that Hume wishes to analyze and determine their origin.

First of all Hume analyses the principle of causation i.e. the view that an effect is produced by a cause. For example, consider the example of two striking marbles. The moving marble strikes the stationary marble, and the stationary marble starts moving. What have we experienced? We have perceived two events: 1) The moving marble strikes the stationary marble 2) The stationary marble starts moving. And we perceive the following relations between these two events:

1. Contiguity: The two events are contiguous.
2. Priority: The first event occurs before the second one.
3. Constant Conjunction: The two events occur together as many times as we observe them.

Hume says that we have experienced only these three relations in the above example, and we have never experienced the moving marble causing the stationary marble to move. We have the impressions of two events but we do not have impression of the causation itself; hence, there is no logical basis to believe in cause and effect.

Here the principle of Induction also involves itself. A person may object saying that since in all observations made the two events occur together, we are justified to believe that they will always occur together. But Hume explains that induction is also not based on reason. Consider the example of a stone falling down. Every common man believes a stone dropped will always fall towards the earth, but Hume says that this belief is not rational. Let us inquire: why do we believe that a stone will always fall towards the earth? The answer is that because we have seen this happen millions of times. Hume agrees that we have experienced a stone falling to the ground many times but we have never experienced the stone falling to the ground always. [We have seen it falling to the ground always in the past but we haven’t yet experienced it falling every time in the future.] Similarly, Hume questions why do we believe that the sun will rise tomorrow? It is because we have seen it happen always in the past. But just because an event has always taken place in the past doesn’t mean that it will certainly happen in the future.

The doctrine presented here can be stated in two parts 1) There is no such thing as causality, and 2) The principle of Induction is not a valid principle. For example, if B follows A in all our observations, then 1) A doesn’t cause B and 2) it is not necessary that B will always follow A. We can only say that it is probable that B will follow A, but this probability is not a certainty, and it is always in the danger of being refuted by fact.

Then, Hume comes to the external world. He says that we have never really ‘experienced’ the external world. We perceive only impressions, which we causally assume to be caused by an external object, but we have no direct experience of the presumed cause. And Hume has just shown that causality is an irrational belief. As we perceive objects only by means of ideas, we cannot use them to establish a causal connection between the things and the objects they are supposed to represent. Hence, our knowledge of external world is not based on reason and logic, and there is no reason to believe that the external world exists.

Hume now attacks an age old belief, namely, the belief in the Self. Descartes based his whole philosophy on I think and ‘I’ had an importance in his system. Berkeley too gave a lot of emphasis on mind in his philosophy. But, Hume questions, have we ever perceived our self, or our mind? He answers in negative and says that we have no impression of the self. No matter how closely we analyse our thoughts and mental operations, we never actually experience ‘I’. What we do perceive is a rapid succession of individual and separate ideas, and there is no logical evidence of any sort of their coherence and integrity. Thus, the “Self” cannot enter into our knowledge except as a ‘bundle’ of perceptions! The self is nothing “but a bundle or collection of different perceptions which succeed one another with inconceivable rapidity and are in a perpetual flux or movement.” [This was an inevitable conclusion of empiricism, but Berkeley didn’t proceed to it.]

“If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, "Does it contain any abstract reasoning concerning quantity or number?" No. "Does it contain any experimental reasoning concerning matter of fact and existence?" No. Commit it then to the flames: for it can contain nothing but sophistry and illusion,” Hume states somberly.

These conclusions are certainly disastrous. They logically reduce Hume’s position to that no knowledge is possible by reason. Does this mean that reason can tell us nothing? Is there nothing to be learnt from experience and observation? If not logic, what then are the origins of the ideas of causality, matter and self? Habit, Hume answers. All our reasoning concerning cause and effect is derived from custom. We have been so used to these ‘succession of events’ that they have become a habit. “Custom, then, is the great guide of human life”[1] says Hume. His skepticism has shown that pure empiricism does not give a sufficient basis for science, for the whole of science rests on the idea of cause and effect. The question raised by Hume is not whether the sun will rise tomorrow or not, but why do we believe so? For Hume, we believe in causality because of our feelings, and not because of reason. But feelings are subjective, and this inevitably leads to the conclusion that there is no distinction between right or wrong in these cases.

Is there really no rational basis for the principle of Induction? This principle, when applied to causation, says that if A has accompanied or is followed by B, and no exception to it has been observed, then it is probable that on the next observation A will be accompanied by or followed by B. This principle gives only a probability, and not certainty. Consider, for example, another crude example of induction: we have observed crows many times, and in all these observation the crows are black. From this, we cannot derive the conclusion that ‘All crows are black’, because we have never seen all the crows. We can only say that it is probable that the next crow we encounter will be black, but it is certainly possible that a white crow may exist which we have not yet observed. The only alternative is to accept the principle of Induction as a separate and independent logical principle, not derived from deduction, but this acceptance itself is not logically necessary. Most philosophers are convinced that induction is valid in some degree but the problem of showing how or why it can be valid remains unsolved. We shall deal more with the problem of induction in the chapter on Karl Popper, who is of the view that science is not based on the principle of induction, and hence, is safe from the problem of induction.


[1] Hume, Inquiry Concerning Human Understanding