The traditional understanding of Locke’s famous distinction between primary and secondary qualities has been heavily criticised over the years, but these criticisms can be avoided once Locke’s scientific intention in proposing the distinction is accounted for. In this piece, an account of primary and secondary qualities will be given in the light of the corpuscularian hypothesis. The aim of this paper is not to show that Locke’s thought was identical to the thought of Boyle,[1] but to show that Locke intended this particular part of his work to be understood in terms of the corpuscularian hypothesis. Such an understanding is more intelligible, eliminates many of the traditional objections to the distinction, and explains some textual anomalies.
The central claim of the corpuscularian hypothesis is that all observable bodies are composed of minute particles of matter (corpuscles) with basic properties. Boyle thought these basic properties were shape, size and mobility, and that the variety of observable properties (e.g. colours, tastes etc.) could be explained in turn, by the properties and arrangements (texture) of the corpuscles themselves. He also thought that changes in bodies (of colour, taste etc.) could be explained by the re-arrangement of these individual corpuscles, and that observable interaction between bodies was interaction between their minute particles.[2]
There are three factors that offer support for interpreting Locke in terms of Boyle’s newly developed scientific account: a) language, b) method, c) explanatory power. The main focus of this piece will be on the explanatory power of this interpretation, however, a brief excursion into language and method may help to further support the proposed reading of the text.
Locke’s language and technical terminology is similar to that of Boyle. He uses the terms ‘texture’,[3] ‘quality’,[4] and even ‘corpuscles’[5] in discussing his distinction, all of which are used by Boyle in similar contexts. Both writers also refer to the motion of the ‘minute particles’[6] of bodies when explaining phenomena. Locke’s awareness of the relevant scientific books coupled with the observed parallels in language, generate suspicion that he intended comparison between the views. Further, Locke refers to his distinction as a scientific one when he says ‘I hope I shall be pardoned this little excursion into natural philosophy’[7] in the concluding paragraph of chapter eight.
Read in terms of the corpuscularian hypothesis, Locke’s method also mimics that of Boyle, for he thinks the success of the hypothesis to be demonstrated by the success of its applications to observable phenomena.[8] It seems that the main distinctions between qualities are given in sections 7-15 of chapter 8 of the Essay, and a demonstration of how well they explain phenomena in the physical world given in sections 16-21. Admittedly, proposing and then demonstrating the applications of a hypothesis is a method general to science and not specific to Boyle. However, this reading of Locke’s method is crucial to understanding the distinction in terms of the corpuscularian hypothesis because, contrary to the traditional interpretation, the distinction is being illustrated rather than argued for in sections 16-21. Why this is so important will become clear later when Berkeley
A full understanding of Locke’s distinction must begin in s.7 of the Essay where Locke gives his new, technical, definitions of the terms ‘ideas’ and ‘qualities’. Locke’s predecessors had loosely used the term ‘idea’ to refer to both what was in the mind, and the cause of it in the body.[11] Here these two usages of ‘ideas’, ‘…as they are ideas or perceptions in our minds; and as they are modifications of matter in the bodies that cause such perceptions in us’, are separated out.[12] Locke assigns the term ‘idea’ to ‘the immediate object of …understanding’, and the term ‘quality’ to the affections of matter within the body that can cause such ideas within a perceiver.[13] Hence, having ensured that the reader understands that ‘Ideas are in the mind, qualities in the bodies’,[14] Locke proceeds to distinguish two kinds of qualities; primary and secondary.
Primary qualities (PQs) are ‘utterly inseparable from the body in what estate soever it be’,[15] and can be listed as ‘solidity, extension, figure and mobility’.[16] They are essential to matter, and are thus retained, no matter what changes a body is subjected to. An illustration of this is that if a grain of wheat is divided ‘till the parts become insensible’, although there is observable change, each insensible part will still have its PQs.[17]
Secondary qualities (SQs) are defined as ‘a power to produce various sensations in us by their primary qualities’.[18] Such powers are present within a body due to the arrangement of its corpuscles, or the ‘texture’ of its insensible parts.[19] Importantly, the ‘colours, sounds, tastes’ mentioned in this passage are ideas of SQs rather than SQs themselves.[20] It is not that the SQs are due to the arrangement of corpuscles, the SQs are the arrangement of corpuscles.[21] The ideas of SQs (e.g. colours, tastes etc.) are due to the SQs themselves, which are really present within the body. As PQs characterise everything material, such textures cannot be PQs because individual corpuscles are incapable of having texture.
Traditionally these early passages have been interpreted as providing the ‘separability’, and ‘mind-dependence’ criterions for Locke’s distinction; that SQs are separable from the body and mind-dependent, whereas PQs are not. These are thought to be argued for when Locke claims firstly, that the mind cannot conceive of a body lacking the PQs, and secondly, when he says that SQs are ‘nothing in the bodies themselves’.
Thinking that these were two of the reasons Locke was offering for distinguishing PQs and SQs, Berkeley Berkeley
Interpreting Locke according to the corpuscularian hypothesis, Berkeley
In the final sections of chapter eight, there are several vivid demonstrations of how the application of the distinction between PQs and SQs, can provide explanations for observable phenomena. Several examples are listed by Locke, of which, three will here be considered as each demonstrates a slightly different element of the distinction in terms of the corpuscularian hypothesis.
Firstly, it explains how a body can remain unchanged although perception of it may alter. Examining Porphyry,[25] which is an array of fabulous colour in the light, Locke notes that its colour is lost when the light is switched off, yet re-appears on its return. He thinks it ridiculous to suppose that there is any change in the Porphyry that explains the change in the manner it is perceived. Instead, the ‘whiteness or redness are not in it at any time, but such a texture that hath the power to produce such a sensation in us’. That is, the ideas of SQs (the redness and whiteness), are not in the Porphyry, but are only caused by the qualities of the Porphyry (the relevant SQs). Thus, whether the light is on or off… ‘it has indeed such a configuration of particles, both night and day, as are apt to …produce in us the ideas of redness and whiteness’.[26]
Secondly, it explains why certain activities can dramatically change the properties of a body. Considering an almond that is pounded with a pestle,[27] Locke suggests that the pestle is altering nothing but the texture of the corpuscles, and that this change explains the marked difference in the observable properties of a body.
Thirdly, it explains the appearance of a body’s having contradictory properties, for ‘we may understand, how it is possible, that the same Water may at the same time produce the sensation of heat in one hand, and cold in the other’.[28] Understanding the feeling of heat as an interaction between the corpuscles of each hand, and the corpuscles of the water, then, it can be understood that although the same motion is present to both hands, the difference in each hand explains why they are differently affected. It is thus not how it appears to be; that the water is both hot and cold, but rather that there is nothing like the sensation of heat, actually present in the water.
Berkeley mistakenly believed Locke to here be relating further grounds for the distinction because he appears to claim some sort of infallibility with regards to PQs, whilst discussing the illusory nature of the SQ of heat, saying ‘Figure never… producing the Idea of square by one hand, which has produced the Idea of a Globe by another’.[29] PQs can of course be subject to illusion, and Berkeley
If the evidence already given is not enough to convince the reader of the correctness of interpreting the distinction and method in the way stated, there is still further evidence to suggest that Locke did not rely on this contention to support his distinction,[30] for he himself cites such examples of illusion in the Essay.[31] Furthermore, the passage in question seems only to commit Locke to a claim about figure, not PQs in general, meaning that it is possible that Locke held this claim about figure, but not the other PQs, and thus that it was not a ground for the distinction. If this is not a basis for the distinction, then Berkeley
Locke makes the claim that whereas ‘ideas of PQs resemble PQs, ideas of SQs do not’,[32] and once more Berkeley
One problem for this reading of Locke is that there are some textual anomalies that apparently contradict the lists of qualities that this reading would firmly identify as primary or secondary. Problematically, on some occasions Locke lists ‘texture’, and ‘number’ [ref] as PQs, appearing to dissolve the distinction just drawn. Some scholars (Alexander…) believe that these inconsistencies can be explained with reference to the purpose for which each list is related [ref]. Consider the following.
If the definition of a PQ is really something that is a defining feature of matter, then it is possible to see that there are features of observable bodies that are not features of the corpuscles of which they are constituted.[35] A single corpuscle cannot have any arrangement, and therefore cannot have any SQs, but a sensible object, being made up of a collection of corpuscles, must have some texture, and there must also be a certain number of corpuscles, etc. So, a defining feature of observable material objects is that they have some texture, and this is primary in the sense that it is true of all observable material objects, but not primary in the sense that it does not characterise everything material. This accounts for the varying lists of PQs, though some scholars have opted to interpret Locke as only intending the PQs he originally relates as PQs to be truly primary.[36]
Given the explanatory power of interpreting Locke in the light of the corpuscularian hypothesis, and attending carefully to Locke’s indications within the text, this interpretation seems to be the most plausible understanding of Locke’s intention in distinguishing between primary and secondary qualities. Not only is there is much textual support for interpreting Locke in this manner, but it also allows him to escape much of the criticism that has been levelled at the distinction over the years. Understanding Locke in terms of the corpuscularian hypothesis is most certainly the best way to understand him, and is, I believe, the way that he intended his distinction to be understood.
Bibliography
Alexander, Peter (1985), Ideas, Qualities and Corpuscles, Cambridge
Curley, E. (1972), ‘Locke, Boyle and the Distinction between Primary and Secondary Qualities,’ Philosophical Review: 438-64.
Hall, M. B. (1965), Robert Boyle on Natural Philosophy, Indiana
Jolley, Nicholas (1999), Locke, Oxford
Locke, John (1670), An Essay Concerning Human Understanding, Alexander Campbell Fraser (1959 ed.), Dover : New York
Mackie, J. L. (1976), Problems from Locke, Oxford
[1][1] Peter Alexander (1985), Ideas, Qualities and Corpuscles, Cambridge
[2][2] Supra 1, pp. 15-60.
[3][3] Boyle, in M. B. Hall (1965), Robert Boyle on Natural Philosophy, Indiana Dover : New York
[4][4] Boyle, ibid, p. 155, Essay, II viii.
[5][5] ‘the aggregate of those corpuscles may be farther diversified by the texture resulting from their convention into a body’, supra 3, p. 193. ‘corpuscles’ Essay II viii 21.
The traditional understanding of Locke’s famous distinction between primary and secondary qualities has been heavily criticised over the years, but these criticisms can be avoided once Locke’s scientific intention in proposing the distinction is accounted for. In this piece, an account of primary and secondary qualities will be given in the light of the corpuscularian hypothesis. The aim of this paper is not to show that Locke’s thought was identical to the thought of Boyle,[1] but to show that Locke intended this particular part of his work to be understood in terms of the corpuscularian hypothesis. Such an understanding is more intelligible, eliminates many of the traditional objections to the distinction, and explains some textual anomalies.
The central claim of the corpuscularian hypothesis is that all observable bodies are composed of minute particles of matter (corpuscles) with basic properties. Boyle thought these basic properties were shape, size and mobility, and that the variety of observable properties (e.g. colours, tastes etc.) could be explained in turn, by the properties and arrangements (texture) of the corpuscles themselves. He also thought that changes in bodies (of colour, taste etc.) could be explained by the re-arrangement of these individual corpuscles, and that observable interaction between bodies was interaction between their minute particles.[2]
There are three factors that offer support for interpreting Locke in terms of Boyle’s newly developed scientific account: a) language, b) method, c) explanatory power. The main focus of this piece will be on the explanatory power of this interpretation, however, a brief excursion into language and method may help to further support the proposed reading of the text.
Locke’s language and technical terminology is similar to that of Boyle. He uses the terms ‘texture’,[3] ‘quality’,[4] and even ‘corpuscles’[5] in discussing his distinction, all of which are used by Boyle in similar contexts. Both writers also refer to the motion of the ‘minute particles’[6] of bodies when explaining phenomena. Locke’s awareness of the relevant scientific books coupled with the observed parallels in language, generate suspicion that he intended comparison between the views. Further, Locke refers to his distinction as a scientific one when he says ‘I hope I shall be pardoned this little excursion into natural philosophy’[7] in the concluding paragraph of chapter eight.
Read in terms of the corpuscularian hypothesis, Locke’s method also mimics that of Boyle, for he thinks the success of the hypothesis to be demonstrated by the success of its applications to observable phenomena.[8] It seems that the main distinctions between qualities are given in sections 7-15 of chapter 8 of the Essay, and a demonstration of how well they explain phenomena in the physical world given in sections 16-21. Admittedly, proposing and then demonstrating the applications of a hypothesis is a method general to science and not specific to Boyle. However, this reading of Locke’s method is crucial to understanding the distinction in terms of the corpuscularian hypothesis because, contrary to the traditional interpretation, the distinction is being illustrated rather than argued for in sections 16-21. Why this is so important will become clear later when
A full understanding of Locke’s distinction must begin in s.7 of the Essay where Locke gives his new, technical, definitions of the terms ‘ideas’ and ‘qualities’. Locke’s predecessors had loosely used the term ‘idea’ to refer to both what was in the mind, and the cause of it in the body.[11] Here these two usages of ‘ideas’, ‘…as they are ideas or perceptions in our minds; and as they are modifications of matter in the bodies that cause such perceptions in us’, are separated out.[12] Locke assigns the term ‘idea’ to ‘the immediate object of …understanding’, and the term ‘quality’ to the affections of matter within the body that can cause such ideas within a perceiver.[13] Hence, having ensured that the reader understands that ‘Ideas are in the mind, qualities in the bodies’,[14] Locke proceeds to distinguish two kinds of qualities; primary and secondary.
Primary qualities (PQs) are ‘utterly inseparable from the body in what estate soever it be’,[15] and can be listed as ‘solidity, extension, figure and mobility’.[16] They are essential to matter, and are thus retained, no matter what changes a body is subjected to. An illustration of this is that if a grain of wheat is divided ‘till the parts become insensible’, although there is observable change, each insensible part will still have its PQs.[17]
Secondary qualities (SQs) are defined as ‘a power to produce various sensations in us by their primary qualities’.[18] Such powers are present within a body due to the arrangement of its corpuscles, or the ‘texture’ of its insensible parts.[19] Importantly, the ‘colours, sounds, tastes’ mentioned in this passage are ideas of SQs rather than SQs themselves.[20] It is not that the SQs are due to the arrangement of corpuscles, the SQs are the arrangement of corpuscles.[21] The ideas of SQs (e.g. colours, tastes etc.) are due to the SQs themselves, which are really present within the body. As PQs characterise everything material, such textures cannot be PQs because individual corpuscles are incapable of having texture.
Traditionally these early passages have been interpreted as providing the ‘separability’, and ‘mind-dependence’ criterions for Locke’s distinction; that SQs are separable from the body and mind-dependent, whereas PQs are not. These are thought to be argued for when Locke claims firstly, that the mind cannot conceive of a body lacking the PQs, and secondly, when he says that SQs are ‘nothing in the bodies themselves’.
Thinking that these were two of the reasons Locke was offering for distinguishing PQs and SQs,
Interpreting Locke according to the corpuscularian hypothesis,
In the final sections of chapter eight, there are several vivid demonstrations of how the application of the distinction between PQs and SQs, can provide explanations for observable phenomena. Several examples are listed by Locke, of which, three will here be considered as each demonstrates a slightly different element of the distinction in terms of the corpuscularian hypothesis.
Firstly, it explains how a body can remain unchanged although perception of it may alter. Examining Porphyry,[25] which is an array of fabulous colour in the light, Locke notes that its colour is lost when the light is switched off, yet re-appears on its return. He thinks it ridiculous to suppose that there is any change in the Porphyry that explains the change in the manner it is perceived. Instead, the ‘whiteness or redness are not in it at any time, but such a texture that hath the power to produce such a sensation in us’. That is, the ideas of SQs (the redness and whiteness), are not in the Porphyry, but are only caused by the qualities of the Porphyry (the relevant SQs). Thus, whether the light is on or off… ‘it has indeed such a configuration of particles, both night and day, as are apt to …produce in us the ideas of redness and whiteness’.[26]
Secondly, it explains why certain activities can dramatically change the properties of a body. Considering an almond that is pounded with a pestle,[27] Locke suggests that the pestle is altering nothing but the texture of the corpuscles, and that this change explains the marked difference in the observable properties of a body.
Thirdly, it explains the appearance of a body’s having contradictory properties, for ‘we may understand, how it is possible, that the same Water may at the same time produce the sensation of heat in one hand, and cold in the other’.[28] Understanding the feeling of heat as an interaction between the corpuscles of each hand, and the corpuscles of the water, then, it can be understood that although the same motion is present to both hands, the difference in each hand explains why they are differently affected. It is thus not how it appears to be; that the water is both hot and cold, but rather that there is nothing like the sensation of heat, actually present in the water.
Berkeley mistakenly believed Locke to here be relating further grounds for the distinction because he appears to claim some sort of infallibility with regards to PQs, whilst discussing the illusory nature of the SQ of heat, saying ‘Figure never… producing the Idea of square by one hand, which has produced the Idea of a Globe by another’.[29] PQs can of course be subject to illusion, and
If the evidence already given is not enough to convince the reader of the correctness of interpreting the distinction and method in the way stated, there is still further evidence to suggest that Locke did not rely on this contention to support his distinction,[30] for he himself cites such examples of illusion in the Essay.[31] Furthermore, the passage in question seems only to commit Locke to a claim about figure, not PQs in general, meaning that it is possible that Locke held this claim about figure, but not the other PQs, and thus that it was not a ground for the distinction. If this is not a basis for the distinction, then
Locke makes the claim that whereas ‘ideas of PQs resemble PQs, ideas of SQs do not’,[32] and once more
One problem for this reading of Locke is that there are some textual anomalies that apparently contradict the lists of qualities that this reading would firmly identify as primary or secondary. Problematically, on some occasions Locke lists ‘texture’, and ‘number’ [ref] as PQs, appearing to dissolve the distinction just drawn. Some scholars (Alexander…) believe that these inconsistencies can be explained with reference to the purpose for which each list is related [ref]. Consider the following.
If the definition of a PQ is really something that is a defining feature of matter, then it is possible to see that there are features of observable bodies that are not features of the corpuscles of which they are constituted.[35] A single corpuscle cannot have any arrangement, and therefore cannot have any SQs, but a sensible object, being made up of a collection of corpuscles, must have some texture, and there must also be a certain number of corpuscles, etc. So, a defining feature of observable material objects is that they have some texture, and this is primary in the sense that it is true of all observable material objects, but not primary in the sense that it does not characterise everything material. This accounts for the varying lists of PQs, though some scholars have opted to interpret Locke as only intending the PQs he originally relates as PQs to be truly primary.[36]
Given the explanatory power of interpreting Locke in the light of the corpuscularian hypothesis, and attending carefully to Locke’s indications within the text, this interpretation seems to be the most plausible understanding of Locke’s intention in distinguishing between primary and secondary qualities. Not only is there is much textual support for interpreting Locke in this manner, but it also allows him to escape much of the criticism that has been levelled at the distinction over the years. Understanding Locke in terms of the corpuscularian hypothesis is most certainly the best way to understand him, and is, I believe, the way that he intended his distinction to be understood.
Bibliography
Alexander, Peter (1985), Ideas, Qualities and Corpuscles,
Curley, E. (1972), ‘Locke, Boyle and the Distinction between Primary and Secondary Qualities,’ Philosophical Review: 438-64.
Hall, M. B. (1965), Robert Boyle on Natural Philosophy,
Jolley, Nicholas (1999), Locke,
Locke, John (1670), An Essay Concerning Human Understanding, Alexander Campbell Fraser (1959 ed.),
Mackie, J. L. (1976), Problems from Locke,
[1][1] Peter Alexander (1985), Ideas, Qualities and Corpuscles,
[2][2] Supra 1, pp. 15-60.
[3][3] Boyle, in M. B. Hall (1965), Robert Boyle on Natural Philosophy,
[4][4] Boyle, ibid, p. 155, Essay, II viii.
[5][5] ‘the aggregate of those corpuscles may be farther diversified by the texture resulting from their convention into a body’, supra 3, p. 193. ‘corpuscles’ Essay II viii 21.
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