Locke’s Essay on Human Understanding

John Locke Essay Concerning Human Understanding, Final Edition, 1699 (Original 1690).



… The imputation of Novelty is a terrible charge amongst those who judge of men’s heads, as they do of their perukes, by the fashion, and can allow none to be right but the received doctrines. … The imputation of Novelty is a terrible charge amongst those who judge of men’s heads, as they do of their perukes, by the fashion, and can allow none to be right but the received doctrines.


Locke attempts to prime us to take an ‘enlightened’ and open-minded view of his work. He implicitly seems to recognise Cromwell’s rule, and doesn’t claim to have the final word.

In the final edition he addresses some of the criticisms of the first edition, some of which criticisms seem to ‘have had legs’.

In particular, he writes about ‘determinate ideas’ rather than ‘clear’ ones, but hasn’t completely updated his terminology, leading to some possible confusion.


CLEAR and DISTINCT ideas are terms which, though familiar and frequent in men’s mouths, I have reason to think every one who uses does not perfectly understand. …  I have therefore in most places chose to put DETERMINATE or DETERMINED, instead of CLEAR and DISTINCT, as more likely to direct men’s thoughts to my meaning in this matter. By those denominations, I mean some object in the mind, and consequently determined, i. e. such as it is there seen and perceived to be. …

If men had such determined ideas in their inquiries and discourses, they would both discern how far their own inquiries and discourses went, and avoid the greatest part of the disputes and wranglings they have with others.


This now seems non-controversial.


The ideas no more ‘correspond’ to reality than maps do to territories.


Because men would not be thought to talk barely of their own imagination, but of things as really they are; therefore they often suppose the WORDS TO STAND ALSO FOR THE REALITY OF THINGS.

Much of the chapter is about rhetoric; guidance on the use and interpretation of words.

Book IV: The Reality of Knowledge

Locke develops the negative consequences of the above. In addition he recommends experimentation coupled to ‘mathematical reasoning’ as the most reliable form, to which others can be compared. He includes a discussion of uncertainty, with guidance on how to reduce it.

Chapter xxi: The division of the sciences

1.All that can fall within the range of human understandingis in three categories.

  1. The nature of things as they are in themselves, their relations, and their manner of operation.
  2. What man himself ought to do, as a thinking and willing agent, for the attainment of any end, especially happiness.
  3. The ways and means by which the knowledge of each of those two is attained and communicated.

I think that science [= ‘high-level disciplined knowledge’] can properly be divided into these three sorts.

5. This is the first and most general Division of the Objects of our Understanding.

This seems to me the first and most general, as well as natural division of the objects of our understanding. For a man can employ his thoughts about nothing, but either, the contemplation of THINGS themselves, for the discovery of truth; or about the things in his own power, which are his own ACTIONS, for the attainment of his own ends; or the SIGNS the mind makes use of both in the one and the other, and the right ordering of them, for its clearer information. All which three, viz. THINGS, as they are in themselves knowable; ACTIONS as they depend on us, in order to happiness; and the right use of SIGNS in order to knowledge, being TOTO COELO different, they seemed to me to be the three great provinces of the intellectual world, wholly separate and distinct one from another.

The End



Wikpedia mentions some criticisms of Locke. Some of these may be based on the first addition, and relate to matters which Locke sought to clarify in the later editions.

If knowledge is ‘justified true belief’ then Locke is mostly saying that one can only know one’s ideas, and how they relate: one can only conjecture about any supposed reality. With this interpretation, Locke seems reasonable.


In his History, Russell opines:

Not only Locke’s valid opinions, but even his errors, were useful in practice. Take, for example, his doctinre as to primary and secondary qualities. [Cites Berkeley.] [Yet] it proved fruitful as a souirce of many very important discoveries.

He is always sensible, and always willing to sacrifice logic rather than become paradoxical.

However, it seems to me that the ‘logic’ he was sacrificing is that which was in common usage before his time, not that the more refined logic that he ended up with.

Locke may be regardeed as the founder of empiricism.

Perception, he says ‘is the first step towards knowledge, and the inlet of all the materials of it.’

Empiricism and Idealism alike are faced with a problem to which, so far, philosophy has found no satisfactory solution. This is the problem of knowing how we have knowledge of other things than ourselves and the operation of our own mind.

[The difficulties with Locke’s notion of perception have] troubled empiricism down to the present day … .

A contemporary view

Paul Schuurman, in his doctoral dissertation, quotes Locke’s related works and correspondence, giving a great deal of background, supporting a favourable interpretation of Locke, while acknowledging that it was not the final word.

My Comments

It seems to me that Locke is trying to improve on reasoning based on classic logic and ‘innate ideas’. His criticisms seem sound. As was common, he takes experimentation and Newton’s kind of mathematical reasoning as ‘the gold standard’, along with other reasonings that he regards as equally good.

In particular, Locke distinguishes between reasoning about ideas in themselves, and reasoning about what might ‘really’ lie behind them. He accepts that there is more than just ideas, and the thinker’s intercation with this external reality leads to the perception of objects, qualities and relationships, and in particular theories of ‘causality’. But we can only really know these in so far as they are ideas: we cannot know that they correspond to anything real: they could be an artifact of the way we perceive.

All this seems reasonable. Some of Locke’s remarks seem not fully thought through, or simply overtaken by subsequent developments in logic, but his overall approach seems sound. Indeed, some of the criticisms of that are still commonly held seem to have been addressed by him in the later editions.

As a mathematician, I note that mathematics has moved on since Newton’s day. If we are to follow Locke, maybe we should distinguish between different types of mathematical reasoning and  take the best as our ‘gold standard’? Actually, Locke only mentions arithmetic and geometry, not Newton’s calculus, so in modern terms Locke seems to favour first-order propositional logic., the most severely tested form of ‘mathematical reasoning’. This cannot lead to paradoxes or contradictions. (Or at least, if it did we would amend it! (Compare Berkeley.)

Perhaps more importantly, while for any given single decision Locke’s approach may seem ‘pragmatic’, it seems to follow from his approach that as well as developing theories ‘pragmatically’ one should develop logical theories with which to judge the pragmatic ones, so as to avoid undue controversy and the need for excessive paradigm shifts, whether in science, politics, international relations or anything else.

Dave Marsay

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