Locke

Perhaps the most famous objection to view that all ideas derive from sense experience is that this is impossible. Both Locke and Hume appear to assume that sense experience gives us discrete ideas directly. As first examples of simple ideas, Locke lists ‘Yellow, White, Heat, Cold, Soft, Hard, Bitter, Sweet’ (Essay II.I.3). He supposes that what makes all experiences of yellow experiences of yellow is objective patterns of similarity between the experiences – yellow things all look ‘the same’. For example, he says,

In Ideas thus got [through sensation], the Mind discovers, That some agree, and others differ, probably as soon as it has any use of Memory; as soon as it is able, to retain and receive distinct Ideas. (Essay I.II.15)

This suggests that experiences are already ‘packaged’ into ‘the same’ and ‘different’.

To stay with the example of colour, this just doesn’t seem true. First, the colour spectrum is not divided into distinct parts of red, yellow and so on; it is continuous. Second, there are many shades of yellow; to call them all yellow is to abstract from their individual different shades. Putting these two points together, we realise that acquiring the concept ‘yellow’ is not a matter of copying an impression; no experience comes neatly packaged as an experience of ‘yellow’. To learn the concept ‘yellow’ is to learn the range and variety of colours to which ‘yellow’ refers.

How is this done? In order to learn ‘yellow’, we have to pick out and unify our experiences of the very varied things that are yellow. But if all we have to go on are the many various experiences, how are we able to classify them in this way, distinguishing yellow from not yellow? Well, aren’t all shades of yellow are more similar to other shades of yellow than to shades of any other colour (say, orange)? All we need to do is read off, or copy, our concepts from experience.

We can question this – is the world is already structured by relations of similarity and