Greg Detre
Thursday, 14 March, 2002
primary qualities: e.g. shape, size, number, motion
secondary qualities: e.g. colours, sounds tastes
but drawing the obvious distinction between them presupposes a representative theory of perception
RTP = �a contrast between percepts or sense-data or ideas as immediate objects of perception and material things which are the more remote or indirect objects of perception�
Locke�s use of �idea�: �supposed mental proxies for independent realities� (Ryle)
Locke asserted, though did not invent a PQ/SQ distinction � whether he adopted an RTP is contentious
widely believed that he is wrong about both
defenders (e.g. Bennett) usually argue that he did not hold an RTP, or that it�s separable from his PQ/SQ views
Mackie thinks Locke�s PQ/SQ distinction is interesting and nearly right, that it rests on a defensible sort of RTP
however, Locke is misleading + inconsistent in his presentation of it
Mackie�s presentation of Locke�s views:
�There are material things extended in
three-dimensional space and lasting through time. In this room, for example,
there are several chairs: each of them has a specific shape and size and
position, and is at any time in some definite state of rest or motion. The
group of chairs in this room at any time has a certain number. Also, each chair
is made up of a great many tiny particles which move about rapidly even when
the chair as a whole is at rest. Material things also appear to have many other
properties; they differ from one another, we say, in colour, hardness,
temperature and so on. But the real differences which these descriptions reflect
consist wholly in the arrangement and motion of the tiny particles of which
these material things are composed. Such things are also solid or impenetrable
in that each keeps any other out of the place where it is. There are admittedly
apparent exceptions: for example, water soaks into or through a sponge or a
block of sandstone. But this shows merely that in such large-scale things there
may be spaces between the particles: the particles of one thing or quantity of
stuff may find their way between the particles of another. But each ultimate
particle is completely solid and completely excludes any other particle from
the same place. Thus the properties which material things, large or small, have
in themselves are shape, size, position, number, motion or rest, and solidity.
More exactly, each particle has solidity, each large-scale thing has some
approximation to solidity, each thing large or small has some determinate
shape, some determinate size, is at some place and is in some determinate state
of rest or motion, while each group of things has some determinate number.
Material things interact with one another in regular
causal ways: hence we can say that each thing has various powers. To say that a
certain thing has a certain power is just to say that it would affect or be
affected by another thing of a certain sort in some specific manner. A power is
not the cause of such an effect; rather to have the power is to be such as to
cause the effect. The cause � or more accurately, a partial cause, since the
effect will also depend upon other things
� will be some set of properties, of the sorts already mentioned, of the thing that
has the power: it will generally be, or at least include, some set of such
properties of the minute parts of that thing, of the collection of paticles of
which it is composed. These properties which constitute the cause can be called
the ground or basis of the corresponding power.
Material things also interact with our sense-organs
and, through them, with our minds in ways that give rise to those states in us
which we call the having of sensations and perceptions. That is, material
things have powers to produce sensations and perceptions in us, and these
powers, like any others, have grounds or bases in the intrinsic properties of
the things. Also, our sensations and perceptions have what we can call their
experiential content: we have sensations of pain, heat and cold, and
perceptions of coloured shapes, of rough or smooth and variously shaped
surfaces, of impacts, pressures, and resistances of sounds, tastes, smells and
so on. This experiential content is at most times very complex; commonly we do
not attend to it or talk about it as such, but rather attend to and talk about
the material things, with their properties and what they do, which we take it
to reveal to us; but we can attend to the experiential content itself, and it
is then most naturally referred to by such phrases as �how it looks to me� or
�� feels to me� or .. sounds to me� and so on. This experiential content is
partly as of properties of the sorts already noted as belonging to material
things � solidity and determinations of shape, size, motion-or-rest and number.
I have a visual perception as of a circular shape in what I take to be a saucer
and of which I also have tactual perceptions as of something solid, thin and
concave. But this content is also partly as of other features � colours,
sounds, heat, cold, smells, pain and the the like. Shape, size, position,
number, motion-or-rest and solidity, just as they occur as elements in this
experiential content, can also belong to material things. The saucer can be
circular just as I see it as circular, it can be thin just as I feel it to be
thin, what I see as a group of three chairs may indeed be three chairs. Of
course, we can make mistakes, distortions and illusions can occur. I may see as
elliptical the saucer which in itself is circular, and it may feel thicker than
it is. But we sometimes perceive shapes and so on pretty correctly: material
things often have very nearly the shapes etc. that we see or feel them as
having. And even when we make mistakes, they have other shapes, for example, other determinate properties that belong to
the same determinable (that is, shape in general) as those which occur as
elements in our experiential content. We also commonly ascribe to material things
colours as we see colours, as they occur as elements in our experiential
content, and again heat, cold, roughness and so on as we feel them; we ascribe
tastes as we taste them to bits of food and to liquids, smells as we smell them
to spatial regions; and I think of the ticking sound as I hear it as coming to
me from the clock. But this is all a mistake, a systematic error. All that is
out there in reality is the shape, size, position, number, motion-or-rest and
solidity which occur as properties both of large-scale things and of their
minute parts (though perhaps there is also some substance or substratum to
which these properties belong � see ch 3). It is these properties, especially
those of the minute parts of things, that cause the corresponding sensations
and perceptions whose qualitative content we wrongly ascribe to external
things. On the other hand pain as we feel it, though it may be caused by an
external object, say by a needle sticking into my finger, is not ascribed to
that external object; rather it is commonly ascribed to the part of one�s body
in which, as we say, the pain is felt.�
Locke�s terminology:
idea = �whatsoever is the object of the understanding when a man thinks�
this could include real/external objects of thought, or �concepts� (�phantasms�, �notions�) (or Mackie�s experiential content), imagination or memories
he includes ideas �as they are ideas or perceptions in our minds�
but excludes them �as they are modifications of matter in the bodies that cause such perceptions in us� � Mackie thinks he should use �qualities� to refer to these �modifications of matter� but he doesn�t
is �modifications� just a dated way of saying �properties�???
qualities
= the various powers of objects to produce ideas in us???
but he then identifies as primary qualities: �solidity, extension, figure, motion or rest, and number�
but these are not powers � rather �they�re intrinsic properties of things which may be the grounds or bases of powers, and they are �modifications of matter in the bodies�� (Mackie)
examples of secondary qualities: �colours, sounds, tastes etc.�
these are identified with powers � they are �nothing in the objects themselves, but [except] powers to produce various sensations in us by their primary qualities, i.e. by the bulk, figure, texture and motion of their insensible parts� (Locke)
this is often misread as saying that the secondary qualities are not in the objects at all, only �in the mind�
secondary qualities are meant by Locke as the powers of things to produce ideas in our minds, not the ideas themselves
the distorted view had become the current usage, and Berkeley confuses it too
according then to Mackie, Locke�s �official terminology is that
while there are ideas both of primary and secondary qualities, and all such ideas are in our minds,
the primary qualities are the intrinsic properties of material things, large or small � that is, shape, size, number, motion-or-rest, and solidity �
and the secondary qualities are powers of material things, whose basis is the primary qualities of the minute parts of those things�
�Locke includes under the heading �secondary qualities� both
powers to produce ideas of colours and so on in us
and powers to produce changes in other bodies, e.g. the power of the sun or of a fire to melt wax�
Locke says that shape, size etc. �may be called real, original or primary qualities, because they are in the things themselves, whether they are perceived or no�
this seems to suggest that secondary qualities are the opposite
but to give Locke a consistent view, we have to read this as meaning merely that the secondary qualities are powers to produce (especially) perceptions, not that they are themselves those perceptions/ideas
Locke says that �the ideas of primary qualities � are resemblances of them, and their patterns do really exist in the bodies themselves; but the ideas produced in us by these secondary qualities have no resemblance of them at all�
the point is that even under ideal conditions, colours as we see them are totally different not only from the powers to produce such sensations (with which Locke equates the secondary qualities), but also from the ground/basis of these powers in the things we call coloured
this ground will be only some arrangement + motion of the minute parts of the surfaces of these things
it is
trivial that our ideas of secondary qualities (colours as we see them) cannot
be/resemble powers, but it is not trivial that they don't resemble the grounds
of the powers � this is a non-obvious but (thinks Locke) real difference
between the secondary and primary qualities
primary qualities should be identified with powers � a square object has the power to produce the idea of squareness in me in favourable conditions
but �primary qualities� also refers to the intrinsic features of things which form the grounds/bases of their various powers
the ideas of primary qualities resemble the grounds of the powers to produce those ideas
solidity poses a problem: �solidity � carries something more of a positive in it than impenetrability; which is negative, and is perhaps more a consequence of solidity than solidity itself� � i.e. he wants solidity to be the ground of the power, not the power itself
a primary/secondary distinction could be introduced not as an error theory (i.e. we mistake secondary qualities for primary ones � as Locke offers it), but as an analysis of what we ordinarily think + say
given that we know that a colour looks different in different circumstances + to different people, we may already treat �This is crimson� as the ascription of a power rather than as the claim that there is in the cloth an intrinsic feature that resembles one of our colour ideas
however, Mackie agrees with Locke that our dominant view usually gives secondary qualities much the same status
|
Intrinsic
features of material things = �PQ� |
Powers
of material things |
Items
�in minds� |
|
Shape, size, number, position, solidity, motion-or-rest (i) on large scale = ground of power (i) |
(i) Power to produce ideas of PQ (ii) Power to produce ideas of SQ |
Shapes etc. as we see and feel them = �Ideas of PQ� Colours as we see them, sounds as we hear them etc. = �Ideas of SQ� |
|
(ii) of minute parts = ground of powers (ii) (iii) and (usually) (iv) |
(iii) Power to produce pain, sickness etc. (iv) Power to produce changes in other things _________ Powers (ii), (iii), & (iv) = �SQ� |
Pain, sickness etc. |
if this was
the distinction that Locke was trying to draw, it presupposes a RTP by
contrasting ideas in minds and intrinsic features of external material things
while our
ideas of both primary and secondary qualities correspond to and systematically
represent real differences in external things, it is with the primary qualities
alone that our ideas fairly faithfully depict what is there in the things
argues that fairly close relatives of all the other Boyle-Locke primary qualities still figure among the data of modern physical explanation
�the doctrine of primary and secondary qualities is nothing but some scientific truths dangerously elevated into a philosophical doctrine� (O�Connor)
e.g. primary qualities are merely those in which physicists are most interested, perhaps because they�re most easily measured + formalised
this misses the point � it�s not just that they�re scientifically interesting, but that they show that there�s no good reason for postulating features of a certain other sort (i.e. objective features which resemble our ideas of secondary qualities)
what would be required for us to justify our taking colours to be primary qualities?
1. would want a scientific case for postulating the existence of qualities with the spatial structure of colours, either in addition to or instead of the hypothesised micro-structures which physicists currently refer to in explaining colours
2. need reason to believe that the surface-covering quality of redness looks the same to different (non-colour-blind) people, and that�s verdical (some objective feature to which those judgements correspond)
physics then gives us neither reason for taking colours (etc.) as primary qualities
Locke�s arguments:
1. poor argument:
introduces primary qualities as �such as are utterly inseparable from the body, in what state soever it be; and such as in all the alterations and changes it suffers, all the force can be used upon it, it constantly keeps; and such as sense constantly finds in every particle of matter which has bulk enough to be perceived; and the mind finds inseparable from every particle of matter, though less than to make itself singly be perceived by our senses�
i.e. when a body is changed or divided, it (or its parts), if they are big enough to be seen, can still seen to have shape/size/etc.
and that even if the parts are too small to be seen, we still have to think of them having shape/size/etc.
this contrast seems to depend on an unfair comparison between determinable qualities on the primary side, and determinate qualities on the secondary side
if we carry division to the point where the separate particles are no longer perceivable by the senses, it seems circular to appeal to the fact that the mind will still give each particle some shape + size, but not perhaps, any colour/temperature � if the mind discriminates thus, it will be because it has already adopted the distinction
what is central in the notion of a primary quality is that:
i. it is an intrinsic feature of material things
ii. but is also a resemblance of some idea � i.e. at least of the same category as some features that figure within the contents of our experience
2. better argument � the sensation-effect need not resemble its cause, as when pain is produced by a piece of steel dividing our flesh
3. less useful � Locke talks about how if you pound an almond, the taste + colour change � he asks �what real alteration can the beating of the pestle make in any body, but an alteration of the texture of it?�
but you can answer that the beating could alter intrinsic colour/taste qualities, or just that there might have been differently coloured/tasting liquids shut up in the cells of the nut
4. there is nothing like pain or nausea in the materials that produce them, so why should we suppose that there must be something like colours (etc.) as we see them in the objects that produce these ideas in us?
supports Locke�s notion of a pattern of relationships where some basis in an object gives rise to the power to produce in us a sensation whose content is quite unlike that basis
but doesn't show why colours etc. conform to this pattern whereas shapes/sizes/etc. do not
i.e. that there may be secondary qualities, but not that the line between primary/secondary qualities is necessarily to be drawn where he draws it
5. shows how his theory can explain illusions such as the same water feeling hot with one hand and cold with the other
lukewarm water could produce different feelings (arising out of the changes in motion of minute parts of our �nerves and animal spirits�) in either hand
but he also throws in the remark that shape �never produces[s] the idea of a square by one hand [and] of a globe by another�
careless readers took this to mean that Locke was founding the primary/secondary distinction on the claim that secondary qualities are subject to sensory illusion while primary ones are not (even though Locke himself records illusions that affect primary qualities)
then Berkeley can easily reply that:
illusions also occur with primary qualities
then, adding the further misinterpretation (see above) that secondary qualities exist only in the mind
conclude that Locke (for consistency) must admit that primary qualities also exist only in the mind
the point is that the explanations that corpuscular scientific theory gives of secondary qualities make use of the assignment, to the powers to produce the corresponding ideas, of bases which do not resemble those ideas, but the same is not true of the explanations which it would give of illusions about primary qualities � these still involve the assignment to material objects of qualities of just the same category as those that occur within our experiential content
Mackie contends that Locke�s arguments aren't very strong, and the best support for the primary/secondary distinction comes from physical explanation, mostly after Locke�s time
Berkeley�s arguments against:
1. his detailed argument that illusions occur also in our perception of primary qualities is beside the point, since the distinction does not rest on illusions only occurring with the secondary qualities
2. �if you will trust your senses, is it not plain all sensible qualities co-exist, or to them appear as being in the same place? Do they ever represent a motion, or figure, as being divested of all other visible and tangible qualities?�
Mackie thinks it�s an ignoratio elenchi for Berkeley to appeal to the senses and how they represent things against a theory whose point is that things are in many respects not as they are sensorily perceived
3. �it is impossible even for the mind to disunite the ideas of extension and motion from all other sensible qualites�
i.e. we cannot even conceive an extended moving thing without giving it some colour or some other secondary quality
if this is just an extension of the second argument, that we always experience extended things as having either colours-as-we-see-them or tactile surface qualities as we feel them, it�s not surprising if our imaginations are similarly restricted
but the deeper conceptual problem:
all of Locke�s primary qualities (shape, size, texture, motion-or-rest and number) are all just aspects of the spatio-temporal patterning/distribution/arrangement of some stuff(s)
they�re incomplete, without something that occupies some spatio-temporal regions and not others
i.e. it would be useless to draw the boundary of a certain shape if there were no difference between what was on one side of the boundary vs the other
but what about solidity? it�s not a purely geometric feature � could it be the item of which each specific extension is the extension?
but as Hume forcibly pointed out, if solidity is just impenetrability, the power to exclude other things of the same sort, it cannot do this job
if two things are to keep each other out of the regions they occupy, each must be not only something other than just a specific region, but also something other than the ability to keep others out of that region
but Locke�s view of solidity is not just impenetrability � it�s not just a power, but the ground of this power
but if solidity is the space-filling feature which makes the difference between body + empty space and enables each body to keep other bodies out, then we do not have a simple adequate idea of it, but only the indirect + relative notion of it as the supposed or inferred ground of a power which is itself learned from its manifestations
i.e. the quality itself doesn't really resemble the idea we have of it, right???
basically the items that:
are meant to be objective features which resemble the ideas to which they give rise in us
is not a complete list of the items that:
a viable physical theory will use as starting-points of explanation
this does not show (as Hume thought) that any of the present secondary qualities have to be taken over and transferred to the �primary� list for the second purpose
the additional basic physical feature(s) will be something that should not be, and perhaps is not, on either the primary or secondary list because it does not appear in our ordinary physical experiential content at all
rather, solidity (like mass or electrical charge) is not an immediate object of any of our senses, so cannot be called a primary quality in the sense of an intrinsic feature of material things which is also a �resemblance� of some ordinary pre-scientific idea
however, the Berkeley-Hume objection does require a revision in Locke�s account of the role of primary qualities
we need to distinguish the two roles that primary qualities play
and to recognise the items that play the second role but not the first
but the objection does not require breaking down the distinction between primary and secondary qualities
but, it may be said, this is the wrong way to develop the objection
whether or not physical theory needs further space-occupying properties, which may well be initially quite unkown to us, we need (for a coherent account of what we perceive + can imagine, so known space-filling property(s) to make the difference between body + empty space for us
this must be one of the secondary qualities (since it can't be solidity, or any of the other primary qualities)
but no � although solidity may not be an adequate candidate for the space-occupying role in for physical theory, perhaps solidity can fill this role for us (i.e. experientially) � e.g. feeling the shape/edge of a physical object without directly touching it ourselves
�Berkeley�s other arguments against the distinction amount to little more than ingenious satire and rhetoric� (Mackie)
this examination has shown up an implausible assumption that Locke makes:
there is little reason to suppose that every real constituent, even basic constituent, of physical things will be recorded in our perceptions � rather, physical theory must postulate at least one constituent feature (to be the extension-occupier) of which no pre-scientific idea that we have is a resemblance
the major difficulty still remains, of the formulation within the framework of a representative theory of perception:
� distinguishes between ideas in our minds and externally real things
� while postulating that our ideas are causally produced by those external things acting on our sense organs
� yet assumes that we can speak intelligibly about resemblances between some of our ideas and those external realities
though we have ideas of both primary and secondary sorts:
� the corresponding realities in the one case resemble the ideas, but not in the other
� the primary qualities really are qualities, and are themselves the ground or basis of the powers to produce the corresponding ideas
� whereas the secondary qualities are mere powers, whose ground/basis is the primary qualities of minute parts
the RTP is widely believed to be untenable, and so fatal for the primary/secondary distinction � see Mackie�s next chapter
distinction between objects of perception which are perceived by more than one sense (often vision + touch), and those which are perceived by only one
coincides fairly closely with Locke�s
Aristotle mentions as:
�common sensibles�: motion, rest, shape, size, number, unity
�special sensibles�: colour, sound, flavour
this carries no commitment to any further theory about their objective status
however, could be considered to be explained by Locke�s theory
since if our idea of some secondary quality is merely a causal product of the interaction of something external with some sense-organ/CNS and does not resemble anything external, then it is on the whole to be expected that it will be peculiar to that particular sense
what about qualities common to both taste + smell (e.g. sourness)?
are these common sensibles? this would then be a primary quality for Aristotle, but a secondary quality for Locke
or you could easily reply that both senses have similar underlying mechanisms, which might be picking up the same ground in the material object
but do the visual + tactile ideas of shape (e.g.) really resemble each other?
Molyneux�s problem = whether a man born blind, who has learned to distinguish by touch a cube and a sphere of the same metal and of about the same size, and who then acquires the sense of sight, would be able to tell which was which of a cube and a sphere by sight alone, before touching them
Locke agrees with Molyneux that the man would not be able to do this
Berkeley developed this, arguing that the visual ideas of them are (intrinsically) quite different from the tactual ones, and only experience enables us to correlate visual with tactual ideas
there is no one common sensible for (e.g.) shape � just a correlated visual + tactile idea (e.g.) of square
this doesn't mean that, by thinking that Molyneux�s man wouldn't be able to tell the shapes apart by sight at first, Locke commits himself to the same denial of shape as a common sensible
this man wouldn't have acquired automatic interpretations of various patterns of shading as indicators of 3D shapes (such as spherical convexity or the corner of a cube projecting towards the viewer)
this leaves open the possibility that 2D shape should be a common sensible for sight + touch
Molyneux�s question raises more than one issue
1. whether Molyneux�s man would be able to say which was which of two flat plates, one square and one circular
2. whether he could tell which was which of a flat circular plate and a sphere
Berkeley would say �no� to both
more plausible to say �yes� and �no�
since a circle is the same all round, whereas a square�s four corners are different from its four sides
in the case of the circle + sphere, there doesn't seem to be an intrinsically common feature to felt convexity and visual shading
Gregory: man who was not totally blind but with no useful vision (from the age of 10 months), whose sight was restored by corneal grafts
he could recognise ordinary objects by sight, tell the time by clock (having learned by touching the hands of a clock, and recognise capital letters learned by touch
but he had vision until the age of 10 months, which might be long enough in the critical window???
the man had no impression of depth from a Necker cube � indirectly supports a negative answer to the second question, although the report doesn't say anything directly
Mackie concludes that Locke could hold that we get the same idea of (2D) shape from both sight + touch
and take Aristotle�s distinction innocently and also as support for Locke�s thesis
however, we have to qualify Locke�s claim that our ideas of shapes resemble the intrinsic qualities of objects which causally produce those ideas, since this will hold for visually + tactually acquired ideas of 2D shape, but may require an unconsciously sophisticated (and learned) performance to form those ideas of 3D shapes which resemble the intrinsic shape-qualities of the things that give rise to them
primary qualities have far more complex, integrated + systematic connections with our experience than secondary qualities
e.g. being size-blind (vs colour-blind) would show up almost at once, unless you suppose a fantastically complicated systematic distortion of his perceptions as opposed to those of other people
it�s more of a contingent matter that we agree on something like taste
e.g. phenol-thio-urea tastes very bitter to 3 out of 4 people, but tasteless to the rest
surgery or selective breeding could bring it about that everyone finds it either bitter or tasteless
secondary qualities do have some causal connections with other aspects of our experience
e.g. red apples are more squashable than green ones, different colours reflect light of different wavelengths etc.
a primary/secondary distinction based on degree of causal connectedness would be very different from Locke�s
Bennett�s distinction is of degree only, not of kind/status
it gives primary qualities a special importance in a scientific/causal explanation of the world, but it would not lead to the conclusion that material things can be completely described in terms of primary qualities (including those of their minute parts) alone
Bennett distinguishes Locke�s:
analytic thesis = a statement attributing a secondary quality to a thing is equivalent to a counterfactual conditional, of the form: �If x stood in relation R to a normal human, the human would have a sensory idea of such and such a kind�
i.e. equates secondary quality statements with attributions of powers to things
causal thesis = �in a perfected and completed science, all our secondary-quality perceptions would be causally explained in terms of the primary qualities of the things we perceive�
Mackie:
the analytic thesis is not true � this is just not what ordinary secondary quality statements naively used mean
it is what Locke is proposing they should mean
why should we give this sort of meaning to secondary quality statements but not give a similar powers meaning to primary quality statements?
Bennett thinks his distinction between degrees of inter-connectedness would justify this discrimination
Mackie thinks that all it would justify is a many-track/multiply-manifested meaning for primary qualities vs a single-track one for secondary qualities
to justify giving a powers meaning to secondary but not primary quality statements requires something more like a causal thesis
if the causal thesis were true, the literal attributions of colours etc. as we see them would be unjustified, and would need a powers meaning
i.e. the causal thesis supports the analytic thesis (better than Bennett�s distinction of degree would) � thus Locke�s distinction is important + of interest but speculative + controversial
the phenol argument supports Locke�s distinction rather than Bennett�s � if bitterness (or colour) are not actually in the things (as some single quality or objective resemblance)
strong case for the Locke-Boyle distinction between primary and secondary qualities
relegate solidity to the status of a power
recognise objvely real + physically important properties which are not resemblances of any of our ordinary ideas
is this account undermined though by objections to the RTP within whose framework it�s formulated?
�
Personal identity
do the particles themselves have size/shape???
of course they do � the idea is to reconcile them with atoms, right???
how close is the view that Mackie describes of �powers� to Locke�s, and Hume�s, views???
is he saying that the power is the large-scale properties, and the ground/basis of the power are the small-scale properties which constitute those large-scale properties???
secondary qualities as emergent properties??? supervenient??? emergent vs supervenient???
what differentiates secondary qualities from primary qualities if they�re just the �powers of things to produce ideas in our minds� (Mackie) rather than the ideas themselves???
secondary qualities simply as high-level or emergent properties???
a power is just a causal disposition, right???
at the end of the day, whether or not our ideas of secondary qualities resemble their powers, there is still a systematic relation between them, right??? how is that helpful???
what�s the bit about Locke discussing seeing the world with microscopic eyes??? (II xxi 63, II xxiii 12)
does that mean that Molyneux�s man should be able to tell more complex shapes by sight alone as well, with a bit more difficulty???
presumably � the fact that a square and circle can be distinguished in words makes it easier, but surely isn't different in principle
see Gregory, �Concepts and mechanisms of perception�, pp 65-129 (reprint of Gregory & Wallace, �Recovery from early blindness: a case study� (1963))
is Locke�s thesis about the distinction between primary and secondary qualities basically an epistemological distinction, i.e. yes, primary qualities are about the intrinsic micro-level features of objects and secondary are macro-level, but to a microscopic bug presumably the �primary� qualities would be more obvious� hmmm, how does that help (isn't it confused???), since the big part of Locke�s distinction is the resemblance (or lack of) between our ideas and the intrinsic features� ??? is Locke saying something ontological about the status/kind of primary vs secondary qualities??? apparently yes
---
what does a non-RTP version of Locke�s PQ/SQ distinction look like???
can it be made to work in an adverbial way??? is an adverbial theory of perception the only alternative to an RTP???
surely an adverbial theory of perception is more or less subject to the same problems as RTP, because even though there�s no specific intermediary (even though the RTP intermediary makes no sense in a modern, i.e. non-Cartesian, conception of mind anyway) between our minds and the outside world, who�s to say that our �seeing catly� is isomorphic (let alone genuinely resembling) the external object???
is it really intelligible to talk about resemblances between some of our ideas and external reality anyway??? I mean, external reality could be mad and quite unlike our sensory representations of it
does colour blindness play any role in the PQ/SQ distinction??? does motion blindness cause any problems for Locke???
�all of Locke�s primary qualities (shape, size, texture, motion-or-rest and number) are all just aspects of the spatio-temporal patterning/distribution/arrangement of some stuff(s) - they�re incomplete, without something that occupies some spatio-temporal regions and not others� � not necessarily � surely Locke could allow for different types of atoms or different structures of atoms (as chemistry eventually discovered) to mark boundaries (although of course he didn't have the scientific know-how at the time)???
ah yes, see Mackie�s point about the two roles for PQs, one of which goes beyond Locke�s original specification and is not sensed by us (hm???)
do taste + smell have similar underlying mechanisms (they�re both vaguely chemical, aren't they�)??? are these the only example of �common sensibles� for Lockean secondary qualities???
I explain Aristotle�s distinction between primary + secondary qualities in terms of forming a multi-modal representation of �primary qualities�, and so you�d expect them to be closer to the real world (assumign there is one) � what implications does this have for Locke�s theory???
why does Mackie say that the analytic thesis is not true (that this is just not what ordinary secondary quality statements naively used mean)???
and for the causal thesis, surely we�d need to include our perceptual mechanisms + brains in our complete scientific description too???