Hume’s take on the relationship between sensations and ideas is true to his usual style: clear and bold yet careful. His prose leads you step by cautious step up through an argument as though it were the most familiar route ever. Only on occasion does he spin you round and you realise with a jolt how far you’ve climbed; how distant is your starting point.
Section II of Hume’s Enquiry concerning Human Understanding offers no such surprises, although there is an uncharacteristic stumble that Hume seems to assume will go unnoticed. He sets off steadily with the claim that immediate perceptions (impressions) are more vivd than even the most vibrant of ideas; recalling the sensation of pain is nothing compared with having a smouldering cigarette end stabbed into your arm (my example, not Hume’s).
Ideas are nothing but the recollection and recombination of impressions. Our ability to shuffle impressions into combinations other than those in which they were first produced gives us an incredibly advanced faculty of imagination. New worlds are opened up: “the thought can in an instant transport us into the most distant regions of the universe; or even beyond the universe, into the unbounded chaos, where nature is supposed to lie in total confusion.”
The one counterexample Hume considers is dismissed as insignificant. It seems that we are able to form ideas of colour-shades that have not yet been impressed upon us. Having seen only two blue objects – one light blue and one dark blue – we can easily imagine a shade between the two. This also applies – Hume tells us – to pitches of sound, and presumably also to intensities of pain and maybe taste.
In fact Hume doesn’t use the phrase ‘intensities of …’. If he had thought in these terms, he might well have escaped his own counter-example by dividing the simple notion of a ‘shade’ into the notion of combined colour and intensity of light. The idea of an unperceived shade is formed by the re-combination of colour-impression and intensity-impression. (As distinct from the idea of an unperceived hue formed by the combination of one colour-sensation and another.)
Interestingly, the earliest use of ‘intensity’ in this sense cited in the OED is attributed to James Hutton in 1794, eighteen years after Hume’s death. Perhaps Hume had in mind the right idea, but science had not yet provided the tools allowing its communication. This might be why he chose to take so little notice of such a stark – if accurate – counterexample.
That our ideas are restricted by past experience is for me the most striking thought. Maybe it should prompt us to rethink how we educate children; how we develop their capacity to entertain abstract concepts. Hands-on learning has for a long time been a buzz-phrase, but Hume gives fresh importance to this style of education. Not only does a broader range of perceptions give us access to more ideas, but a greater experience-base of emotions does too.
The selfish heart, unable to “easily conceive of the heights of friendship and generosity”, will have a hard time coping in a world where others base their relationships on these sentiments. Emotional enlightenment should be given thought along with every other form of education if we are to end up with capable, well-rounded members of society.