To: Max W.
From: Geoffrey Klempner
Subject: Locke's account of simple ideas
Date: 1st April 2011 12:58

Dear Max,

Thank you for your email of 21 March, with your essay for the University of London BA Modern Philosophy: Locke, Berkeley, Hume module, in response to the question, 'What kind of idea is a simple idea according to Locke?'

Reading your essay, I tried to imagine how sense I would be able to make of the distinction between 'simple' and 'complex' ideas, if I had never heard of Locke, or the idea of 'empiricism'. As you state, Locke didn't invent this distinction, it was widely accepted and has been used by many philosophers, before and since. But what is it's *point*?

This simple-seeming question invites two very different kinds of answer. You have gone into some detail in expounding what Locke says about simple ideas. He gives examples. He makes statements which are intended to enable us to categorize ideas under the headings 'simple' and 'complex' for ourselves. And as you also observe, a considerable part of this is problematic.

Take colours. I don't think that it is quite correct to equate the 'many different shades' of the rose with 'perception of different wavelengths of light'. We need to separate two different questions. One concerns the distinction between 'ideas' of colour as such, and the other concerns the best scientific theory that we have to account for our experience of colours. It turns out that according to that theory -- that visible light consists of electromagnetic radiation ranging in wavelengths -- the very same experience of colour, say, yellow, can be produced by a single wavelength, or by a combination of wavelengths. To determine whether or not you are seeing 'monochromatic' yellow (say, as produced by sodium light) you would need the appropriate instruments. You couldn't tell by the eye alone, because the same 'cones' in the retina are stimulated whether the yellow light is monochromatic or not. In another possible world, the explanation for the phenomenon of light might have been quite different, even though our experience of colours was the same.

What Locke is concerned with is the initially plausible idea that if you had never before seen yellow, say, you could not 'imagine' this colour for yourself by any 'quickness or variety of thought'. And yet, as Hume famously noted, we have no difficulty in imagining the missing shade in a range of shades of a given colour (Hume gives the example of blue). What we would now say is that in order to be able to form the idea of a given shade of blue, it suffices that you have the idea of blue as a 'determinable' concept, the given shade being one of its indefinitely many 'determinates'.

This saves the simple/ complex distinction from what seems at first a fatal counterexample. But we still have the problem of deciding which colours you have to experience in order to have an idea of, and which colours you can imagine for yourself. As you note, this isn't in itself a decisive objection because Locke is concerned with the point of principle.

Locke's distinction between simple and complex ideas has a point. The quote about 'quickness or variety of thought' is crucial because even though we can't use this directly as a criterion to decide whether an idea is simple or not, it gives the rationale for the distinction. As a matter of fact, we do possess an impressive ability to think up 'ideas' for ourselves. But this ability presupposes that other ideas, the 'building blocks' are given in experience.

However, this aim is overlaid, and somewhat confused, by another concern which you talk about in your essay, namely, the question of our 'certainty' that the ideas we experience represent something outside us. Surely, it is an obvious non-sequitur (I'm not saying this is a non-sequitur which you commit) to infer from the fact that I am experiencing an idea which I could not have invented for myself by any 'quickness or variety of thought', to the existence of a real object outside me which my idea represents, and which causes me to experience this idea. Obviously not, because an evil demon could have produced the idea in me. I don't believe that Locke commits this fallacy. His position is what you term the 'common sense' view. Doubts about evil demons are fantastical and don't need to be taken seriously. Now, lets get on to the important stuff.

So what is the 'important stuff'?

Right at the beginning of his essay, in his 'Epistle to the Reader', Locke explains why he wrote the Essay. He and a group of friends were having a discussion and couldn't agree because of a confusion about ideas. Such obstacles in the way of knowledge can only be cleared by the philosopher, who patiently unravels the source of all our ideas, their root in experience and the various mechanisms by which the mind compounds them. Although he doesn't exactly state this, the implication is that if this project could be carried through there would be no reason to disagree, ever again about anything except the scientific facts. At that point the philosopher bows out.

All the best,

Geoffrey