My daugther Lola exploring the OBSERVER by Isolde Venrooy at Onzichtbaar Landschap 2019.
Is the question of the existence of colour a philosophical enterprise?
According to our everyday experience, the objects that surround us are coloured. Lemons are yellow, cucumbers are green, and our car is black. But according to physical science, lemons, cucumbers, and our car are composed of particles that are not attributed with colour whatsoever.1 These two pictures of the world seem not entirely compatible, but how come? Is philosophy able to provide us with an answer to this question?
In The Quest for Reality, Barry Stroud argues that there is no such thing as a positive account of the proof for the existence of colour as a property of objects in reality. Stroud denies that we can give any sufficient philosophical arguments to establish such beliefs. An affirmation of our beliefs and experiences of colour would require an affirmation in philosophical terms of the possibility of giving necessary, sufficient arguments as to why colours do exist. The conclusion of Stroud’s metaphysical quest for an understanding of colour beyond our beliefs and experiences, is bound to be, as Stroud says himself; ‘disappointing’,2 because the question of whether colours exist or do not exist cannot be provided with an irrefutable answer by philosophy.
Introduction
The quest for reality, which Stroud has set out for himself, is not a particularly new one. Since ages ago, philosophers, scientists and other thinkers have been agonizing about the question of what is in the world as such, and what part of our experience of the world is due to our human perspective on it. But not only in philosophy is there a lack of irrefutable arguments concerning the existence of colours. To this day, there are as many scientists and philosophers who deny the existence of colour in objects, as there are those who ascribe colours as properties to objects.3
As Mazviita Chirimuuta, author of the book Outside Colour writes; “Of all the properties objects can have, colour hovers uneasily between the subjective world of sensation and the objective world of fact”. 4 This quote demonstrates exactly why the philosophical quest for the existence of colour is a metaphysical enterprise: we cannot escape our own beliefs and perceptions of colour, and yet we want to find a reality beyond our beliefs and perceptions in order to prove the reality of colour in objects.
It is extremely difficult, however, to distinguish the ordinary question from the metaphysical question, and, moreover, there is the question of whether we can meet the requirements of a positive metaphysical theory of colour. After all, Stroud has deliberately been reluctant to offer a positive confirmation, because according to him, we can only expose beliefs as untrue. But although Stroud expresses many reservations about the enterprise of the metaphysical quest itself, the final judgement of Stroud is not to abandon the quest for reality, and I would like to underline his conclusion. The answer to a philosophical question is not limited to whether something is real or not; we want to understand what the structures are behind our perceptions and how our beliefs relate to the world around us. In this essay, I will argue, along Stroud’s arguments, that these different perspectives on the existence of colour in objects is not just about the existence of colour, but about a wider perspective on questions about human perception: how objects appears to us and which beliefs we hold about the objects around us. In the first part of this paper, I will explain what Stroud means by ‘unmasking the unmasker’ and try to elaborate his goal behind this project. In the second part, I will discuss some objections against Stroud, concerning the ‘understanding’ of the conception of colour, raised by Paul Boghossian, Justin Broackes and Ralph Schumacher. I will argue that the way these three philosophers conceive ‘understanding’ of colour, incompatible with the ‘understanding’ that Stroud is aiming for in his quest on reality. The question a philosopher may ask about reality can seem exactly the same as ordinary questions, but are different in approach and I would argue also a different kind of ‘understanding’. In the third part, I will conclude with an argument for why the question of the existence of colour is a metaphysical enterprise. I would argue that philosophical questions embody a certain kind of curiosity towards the world, with which we aim to get to know the structures of the world that lie behind normal appearances. Moreover, I want to argue that a negative account of this question is not bound to ‘disappoint’ us, as Stroud warns us for.
Unmasking the unmasker
The most notable criticism by Barry Stroud in The Quest for Reality is aimed at the eliminativist theories of colour, according to which no objects, in whatsoever form, have any of the colours we perceive them to have or believe them to have. The error theorist holds that all our beliefs and perceptions of colour are false in order to try to unmask the believers of colour existence.5 However, the error theorist cannot deny that we do perceive colours and that we attribute them as properties to objects. As such, Stroud argues that the error theory is self-defeating and aims to unmask the unmasker: if we follow the error theory, we have to take into account the fact that we do perceive colours. The central question for the error theorist then becomes: is it possible to acknowledge other minds as perceiving colour and having beliefs about them without assuming the existence of colour, or any of the beliefs we have about colour? According to Stroud, we could not preserve that we have perceptions of colour and beliefs without affirming that (some) objects are coloured.7 Stroud concludes that holding our colour beliefs is quite independent of their being true. However, we should consider that unmaskers indeed believe that physical objects are not really coloured; Stroud in turn, therefore, attempts to unmask the unmasker and question the possibility of maintaining this position, because it involves a meta-perspective which is detached from our everyday experience of being able to compare our beliefs about the properties of objects.
The veil of perception
According to Stroud, there is a significant difference between answering a question like; “are lemons yellow?” in an ordinary sense and in a philosophical sense. If someone with normal colour vision looks at a lemon in normal daylight, the lemon will appear to have a property which we refer to as ‘yellow’. Stroud argues that in the ordinary sense it is true that lemons are yellow, and cucumbers are green, and tomatoes are red. And indeed, this kind of colour realism which states that objects are coloured, and colours are real, claims that “physical objects are coloured and that colours are physical properties”.8 But, colour realism initially has nothing to do with the understanding of colour, nor is it about how we define colour in language or the semantics of ‘yellow’ and ‘yellowness’. The investigation of colour realism in a philosophical way relates to certain properties that objects appear to have visually, not how the colour words are used or how the conceptualization of colour categories takes place in ordinary daily conversations. The problem with colour realism emerges when we approach the question from a philosophical point of view, as two questions arise immediately: do objects really have distinct properties like colour? And, what are such properties?
There can be very big differences between the properties an object visually appears to have, and the properties it really has. There are numerous examples that demonstrate that our perceptions are not accurate in relation to reality. For example, when we look at a straw in a glass of water, from a certain perspective it seems bent, while, in reality, this illusion is due to the water bending the light, which ‘bends’ the straight straw in our perception. Another example is this dress which went viral on the internet because half of the people who saw a black and blue dress and the other half perceived it as a gold and white dress. So, when we say: “This dress is black and blue”, does is really have the properties of black and blue?
This kind of example, as well as a whole lot of visual illusions, might point out that unless there are necessary connections between our psychological states and the non-psychological facts that they represent, then we can never vindicate our ordinary experiences of and beliefs about the colours of objects. There seem to be a certain ‘veil of perception’, which hides the metaphysical knowledge that we are after. How could we move beyond this stalemate?
Depending on the appearance of properties of objects, we attribute properties to objects like colour or form. When we do this according to the traditional distinction between primary and secondary properties, such as Locke established, colour should be a secondary quality of objects, since colour is a property that seems not to be independent from our perspective ─ as we have seen in the examples above. The form of an object is a property, however, which is independent from our perspective, and as such belongs in the primary realm of properties of objects. The reason to point out this classical distinction between primary and secondary properties of objects, is to draw attention towards a broader perspective on the distinction between these two realms of qualities: it has become the basis to assume that it is at all possible to ‘unmask’ our experiences and beliefs about colour, or about particular properties of objects. 9
But could we unmask our beliefs? As mentioned before: the experiences and the beliefs we have about the colours we perceive are necessary conditions for identifying the psychological phenomena that the unmasker of colours point out to be systematically incorrect.10
Absolute conception of the world?
The question then arises how these two components of the beliefs we maintain and reality relate to each other? Stroud concludes that maintaining our commonsense ideas about colour is quite independent of factual truth; perhaps we should consider that unmaskers do indeed believe that physical objects are not really coloured. If so, the unmasker project requires an engagement with and at the same time a detachment from our beliefs of colour. For example, the unmasker might confess that she believes objects are coloured and at the same time she does not believe that objects are coloured. Stroud questions the possibility of holding this position, because it requires a meta-perspective on our beliefs and experiences, apart from our normal perspective, to compare our beliefs about the properties of objects.
Stroud argues that we cannot judge our perceptions and beliefs as separate from us; we are one with our perceptions and beliefs and therefore an objective judgement about them is not possible. In consequence, the unmasker has to acknowledge these established psychological facts, which in this case would require a detached perspective on his beliefs about the colours of things in order to reflect on them and, simultaneously, an engagement with the very same belief, in order to be able to reflect upon them. But how do you determine the conception of reality, while being unable to circumvent your own subjective view on the world? How to decide on what the relevant difference is between psychological and non-psychological reality? As a starting point, we would need a perspective with beliefs and perceptions that represents the world as it is, apart from us.11 But how to determine such a starting point? Would it be sufficient to exclude colours from the world, but not ‘objects’ like form and numbers? How can we know for certain that numbers and shapes are part ofreality independent from us? In other words: can we reveal the reality which is behind the veil of our perception?
When we think of this last question, two statements come to mind: the world is whatever is the case, or the world is whatever we think it is the case.12And Stroud has made it clear that making a distinction between these two statements is not a straight forward feasibility. We cannot unmask the unmasker from the inside out, so to speak; we cannot use the security of our inner mental life and take this as a starting point through which we can move through logical arguments to knowledge of the external world. To escape the dilemma, we need an absolute conception of the world, which is independent of our perceptions.
But Stroud argues that the quest for this conception would certainly fail, as the absolute goes beyond of our psychological states, hence it cannot explain our psychological states as such. As Stroud argues that we cannot escape our own psychological state of affairs, it seems that once again the answers to these questions will be that the existence of colours is reliant on their perceivers; colours are subjective and we cannot know anything beside that which is spawned by our minds. But how then to proceed with the metaphysical quest of moving from appearance to reality? How can we justify ascribing colour perception to others?
Understanding colour
A response to this question came from the philosophers Boghossian and Schumacher, as well as Broackes. In general, these philosophers are of the opinion that there is no need to perceive colours in order to understand them, or at least to get a grasp of what colours are about. According to Boghossian, it only takes understanding of how things look to other people in order to be able to ascribe mental states about colour to them.13 The term ‘understanding’ is very important here, because it explains why the argument of Boghossian, Byrne and Schumacher misses the point; Not necessarily concerning the quest on colour but concerning the quest on the metaphysical understanding on reality.
According to Boghossian, colour is an experience which is in a constant flux and there is no need for the conception of yellow as a property of physical objects to have the conception of a certain kind of visual experience. Imagine that I have no conception of yellowness, and someone tells me that the distinctive property of the lemon in front of us is what we call ‘yellow’. I would ascribe yellow as a property of the lemon; I do not need to assume the lemon actually has the property of yellow.
We could extend the same line of argument of the example of Broackes to the example of someone who is blind gaining an understanding of what yellowness is, only by the explanation of ‘yellow’ as such: it is a physical property denoting a certain way of reflecting light and it is a disposition of yellowness which has to produce certain sensations in perceivers in order to be recognized as yellow. Broackes points out that this quasi-understanding must be enough in ordinary situations in order to ascribe colour perception to other minds. The distinctiveness of the colour as a property helps to identify it as the property of colour, we do not need to believe in such a property ourselves in order to refer to it, or to gain a quasi-understanding of it.
A last and very convincing example follows from Ralph Schumacher, as he states that we can explain the meaning of colour predicates to a blind person who is: Not able to see the colours and has never seen them, and thus also believes herself to be seeing colours. If we could do that, then we should also regard it as possible that the blind person could get a grasp on the truth conditions of colour predicates. Hence, it should also be possible to explain the colour predicates to an error theorist who does not attributes predicational colour perceptions to themselves nor to other people. 14 Although all counter-examples have some kind of advantages to them, due to the intuitionistic approach of ascribing colour perception to other minds, I think this ‘quasi-understanding’ of colours, as we understand the concepts of a unicorn or golden mountains, does not meet the
requirements of the metaphysical understanding Stroud is after. The metaphysical quest is about moving beyond the quasi-understanding and, I would also argue, beyond the ‘grasp of the truth conditions of colour’ as explained by Schumacher. Although Stroud may accept these kinds of conceptual understanding in the everyday understanding of colour, I would argue that Stroud would reject this approach of the understandingof colours in a metaphysical sense. To summarize the outlines of the objections: the arguments neglect the fact that we should differentiate between looking and perceiving. 15 We can simply look at things, but in the case of epistemic perception, it is required that the perceiver already has a conception of what is seen and therefore some kind of understanding of what colour is, as we cannot know what we are not aware of; the perceiver needs to recognize what he is looking at.
The concept of colour
Indeed, we have every day beliefs about the existence of colour, but the existence and even the inescapability of these beliefs and experiences are not enough to meet the requirements of Stroud’s metaphysical quest for the existence of colour of objects in reality. Answering ‘Do you know this lemon is yellow?’, one might frame this inquiry as needing to be answered from a sceptic Cartesian perspective, or it might be sufficient to answer with a simple ‘yes’.16 It depends on the context of the question, and it is clear that Stroud acknowledges the difficulty in distinguishing philosophical questions from ordinary, everyday questions and, moreover, the differences in sufficiently explanatory answers. I would argue that this pragmatic turn makes the difference between Stroud’s position and the perspective of the sceptic; when you ask ‘Is this yellow?’ to an ordinary fellow human being, the differences in understanding of a concept are small and not noticeable in the given answer. The differences do not stand out to us and, thus, it is not very clear that different concepts of colour are involved. But if we want to deepen our understanding of the existence of colour, this is another step in the conceptual understanding of colour. Wittgenstein asks himself, in order to make ‘further specification’ in concepts of colour, what it would be that makes the difference if people perceived colours which people with normal vision do not know.17 The colour-blind, for example, could easily understand the premise of colours, but could not use the colour words as we could. This is not a difference in complexity of the concepts, but it is a difference in practice and therefore also in understanding. It will get increasingly more difficult when we want to specify more about the concept of colour, in order to find resemblances of the concept of colour in other concepts.
Can we really understand the concepts expressed by a human whose life is entirely different from ours? To be able to do so, Wittgenstein claims, we must be able to describe and understand the imagined practice in which those concepts are used. But the understanding and use of a description already presupposes the pre-understanding and pre-conception of the understanding. Stroud mentions the following quote of Wittgenstein:
“I say to B: “A cannot learn to play chess” B understands that. – But now I say to someone who is absolutely unable to learn any game: so-and-so cannot learn how to play any game. What does he then, knows about the nature of the game?” 18
So, in order to understand what someone is saying when uttering sentences referring to colours, unicorns or golden mountains, we must have an idea, a concept, of the ‘language games’ these concepts figure in, in order to know what they are talking about. I will not go too far in depth into the Stroud’s response to Wittgenstein, but Stroud seems uneasy with this argument ‘from inside competence’, and states that exactly this understanding of conceptual practices is the cause of the difficulty in understanding the concept formation in other people.19 The transcendental arguments Stroud is after rely on premises that do not start with beliefs about the external world, nor about other minds. Instead, Stroud focuses on enabling necessary conditions of coherence experiences or common knowledge; that lemons are yellow would certainly be true in ordinary sense, and the sceptic cannot deny our psychological state of affairs in their endeavour of questioning the existence of colour to begin with. In order to ascribe mental states, such as the experience of colour, to other minds, we could use the following transcendental argument:
“1) Some proposition Q about our mental life, the truth of which is immediately apparent; I make judgements about myself having questions about the existence of colors.
(2) The truth of some extra-mental proposition P is a necessary condition of Q; I could not make judgements about the existence of colour without having experienced or having a concept of colour.
(3) Therefore P; I believe in the questions about the existence of colour.”20
The crucial point is that Stroud, along the lines of Wittgenstein, argues that we need to have concepts of the colours in the first place, in order to question them. Of course we could imagine that other people have different colour experiences than we do, and I would argue Stroud would also agree that we can, in this sense, get a quasi-understanding of the colour perception of other minds. However, it would not work the other way around, as Stroud shows with a quote of Wittgenstein in Seeing, Knowing and Understanding that we cannot imagine that people do not have a conception of colour.21 This argument is crucial according to Stroud, because we have to recognize the different concepts of colour we conceive of, in order to acknowledge the imagined possibility of the conception of our colour perception being different then what they are. We could not make sense of people who do not have a conception of colour, because we must rely on what we do know and how we currently understand things.
According to Schumacher, two possibilities arise concerning the understanding of colour, each with its own implications. Firstly, we may accept that ‘yellowness’ in a conceptual sense comes before the concept of ‘yellow’. If we accept this, then the consequence would be that an understanding of how colors appear to us is enough to understand what colour predicates. Or, we need the concept of ‘yellow’ prior to the appearance of yellow, in order to recognize it as yellow and to maintain the objectivist vision on colour. When we accept the conceptual sense of colour, we accept the examples of Boghossian, Broackes and Schumacher, and settle for how colour appears to me as being enough to understand the nature of colour. Or, when we reject the understanding of colour offered in the counter-examples, then we would need the concept of colour first, in order to grasp an understanding of colour, which would have as a consequence that the blind as well as the error theorist are both in a position to understand the concept of colour. Ralph Schumacher concludes that we could indeed acknowledge that; “The colors of things are like unicorns and golden mountains, that we can acknowledge that people believe in without having ourselves to accept their existence”. 22
And since I have argued for a deeper understanding of colour with regard to the metaphysical quest of Stroud and the simplistic ‘understanding’ of Byrne, Broackes and Boghossian, I would argue that we indeed need at first a concept of colour in order to question the perception we have of it. But, with regard to the objections of the perception of colour by other minds, it must be acknowledged that a contextualist approach of the word ‘understanding’ is required to make sense of this: the utterance of ‘understanding of colour as a property of objects’ has different meanings when in a quasi, everyday kind of understanding or in a metaphysical understanding, which Stroud is after. It would be sufficient to say that other minds indeed can have an understanding of the conception of colour, without holding a firm belief of the existence of colour. But it would not be enough to evade the main claim of Stroud in which he defeats the error theorist in that there is a metaphysical belief in colours and at the same time there is not a metaphysical belief of the existence of colours.
In addition, Stroud argued that, to any claim about the truth of a necessary condition of our mental life, the sceptic can always refute the necessity of the truth of the claim, bringing in it is sufficient for us to (only) to believe it to be true. But the sceptic could not reduce the belief or existence of something questioned like the existence of colour. And if thoughts about the colour of objects cannot be reduced to something else, it couldn’t hold that there are persons with beliefs about colours and systematically find all those beliefs to be false.23 Hence, if we believed that objects are not really coloured, we wouldn’t recognize the perceptions of colours; we wouldn’t be able to give a description of colours. Stroud concludes that this must presuppose a causal chain of perception and successful reference in relation to coloured objects, in which there has been an adequate reference to colour and colour perception.
Stroud admits that this defense against the sceptic, “(…) does not imply we know the things in question, and it does not imply that they are true. It does, however, imply that “we could never see ourselves as holding the beliefs in question and being mistaken (…)”. 24
Conclusion
In everyday life, we believe that colours do exist, but according to Stroud, the question if lemons are yellow could not be answered positively in a metaphysical sense. Stroud’s aim is “(…) achieving a general philosophical understanding of ourselves and the world.” 25 in which what is ‘really so’ is a view on the world which is not dependent on the human perspective of that world. Stroud is not only aiming at the rejection of the traditional way of thinking about colours as mere ideas or features of ideas in the mind, but also the view that colours are dispositions or powers in objects that produce ideas in us. This conclusion certainly leaves us with questions; colours are supposed to be dependent on being perceived and thus secondaries qualities of objects, but then why is form not dependent on perception? Somehow, Stroud has made a distinction between ‘subjective’ and ‘unreal’, and ‘objective’ and ‘real’.26 It is not entirely clear why he argues for this, and Stroud remains inconclusive about this distinction. On this matter, Byrne fittingly argues: “Let it be granted that colours are constitutively connected to minds, and that shapes aren’t. Let it even be granted that objects are not coloured in worlds with no minds. This doesn’t show that colours enjoy a kind of second-class ontological status. Mental properties are trivially ‘subjective’ or ‘not independent’ of us but are not thereby less qualified to be part of reality. Why is it any different with colour?” 27
I believe this question is justified, and Stroud’s answer, thus, would still benefit from some additional explanation. The doubts raised by the philosophical inquiry into the knowledge of whether the lemon is indeed yellow, tend to be far-reaching in what we believe is true about how the world appears to us. Stroud wants to distinguish between a metaphysical quest and a regular question. Additionally, his answers do not provide clarity on what is supposed to be a philosophical question. In this respect, the conclusion of Stroud has similarities with the sceptical enterprise of Hume, in which Hume strove to eliminate the sceptical challenge but finally concluded with a sceptical theory he himself articulated.28 I do not consider Stroud to be a sceptic himself, but only propose to take his scepticism very seriously.
Another possible way to address this question is from the perspective of the natural sciences, with a purely physical conception of the world, restricted to vocabulary in which colours of objects would not be mentioned. But would that make any contribution to a philosophical answer to the question? Does a physical conception of the world tell us how things are in that world? It seems to me that physical sciences cannot give closure to the question of whether colours are part of absolute reality. Physics cannot give an ‘explanatory sufficiency criterion of reality’, according to which what is part of independent reality is only that which must be acknowledged to be so in order to explain human beings’ perception and feeling and believing everything they do about the world. This shows that there is so much more than only a physical connection; it will include at least all those psychological facts that it seeks to explain.
Stroud’s reply to the wish of knowing absolute reality and, consequently, distinguishing it from our beliefs and perceptions is that we should instead accept the limitations of our knowledge. In this respect, the realist theory and the anti-realist theory have in common that they are not able to answer the question ‘what is beyond our human perception?’ But is there any theory that does? We could never achieve that level of detachment from our beliefs to be able to give a sufficient and necessary connection of that which the metaphysical quest requires. This conclusion does not by any means hold that we should give up on asking ourselves philosophical questions. Stroud’s refutation of the position of the sceptic reaches the core of this metaphysical quest, on that there are questions about beliefs we have: that the examination of the existence of colour is embedded in this broader metaphysical approach towards the world we live in, and that the possibility of a general error with respect to the experiences and beliefs about the existence of properties of objects such as colour is always with us. But this does not mean in any way that we should abandon this mission. An important contribution to this mission is that questions on perception and beliefs are pre-eminently a metaphysical undertaking, and therefore belongs in the realm of philosophy. And so, along the contemplations of Stroud, I have argued that the existence of colour is a philosophical question by any means.
References
Allen, K. (2011). The Quest for Reality: Subjectivism and the Metaphysics of Colour, by Barry Stroud. Mind, 120(480), 1306–1309. https://doi.org/10.1093/mind/fzr090
Bardon, A. (2005). Performative transcendental arguments. Philosophia, 33(1–4), 69–95. https://doi.org/10.1007/bf02652648
Boghossian, P. (2015). Seeking the Real. Retrieved July 1, 2019, from Philosophical Studies website: https://www.academia.edu/825254/Seeking_the_Real
Broackes, J. (n.d.). Stroud and the Quest for Reality. Retrieved from https://www.brown.edu/academics/philosophy/sites/brown.edu.academics.philosophy/files/uploads/ColourWorldAndArchimedeanMetaphysics.pdf
Byrne, A. (2018). Yes, Virginia, Lemons are Yellow. Retrieved July 1, 2019, from Philpapers.org website: https://philpapers.org/rec/BYRYVL-2
Byrne, A. (2019). Review of Stroud, The Quest for Reality. Retrieved July 1, 2019, from Mit.edu website: http://www.mit.edu/~abyrne/StroudReview.html
Byrne, A., Encyclopedia of Cognitive Science, Encyclopedia of Cognitive Science, & Hilbert, D. R. (2000). Colour Vision, Philosophical Issues About. Retrieved from ©Macmillan Reference Ltd website: http://web.mit.edu/abyrne/www/ColourVision.pdf
Dame, N. (2012). The Possibility of Philosophical Understanding: Reflections on the Thought of Barry Stroud // Notre Dame Philosophical Reviews // University of Notre Dame. Retrieved July 1, 2019, from Notre Dame Philosophical Reviews website: https://ndpr.nd.edu/news/the-possibility-of-philosophical-understanding-reflections-on-the-thought-of-barry-stroud/
Harris, M. (2015, May 22). Does colour Even Exist? Retrieved July 1, 2019, from The New Republic website: https://newrepublic.com/article/121843/philosophy- colour-perception
Horácio, Roberto. “Stroud’s and Strawson’s transcendental arguments against Hume.” Academia.Edu, 2015, www.academia.edu/19725184/STROUD_S_AND_STRAWSON_S_TRANSCENDENTAL_ARGUMENTS_AGAINST_HUME. Accessed 5 July 2019.
Keeley, B. L. (2011). Making Sense of the Senses: Individuating Modalities in Humans and Other Animals. Retrieved July 1, 2019, from Philpapers.org website: https://philpapers.org/rec/KEEMSO-2
Ma, Z. (2017). Editor(s): (1) Jan-Erik Lane, Institute of Public Policy, Serbia. (2) Raffaela Giovagnoli. Asian Research Journal of Arts & Social Sciences, 4(4), 1–5. https://doi.org/10.9734/ARJASS/2017/38095
Schumacher, R. (2007). Do we have to be Realists about Colour in order to be able to attribute Colour Perceptions to Other Persons? Erkenntnis, 66(1–2), 233–246. https://doi.org/10.1007/s10670-006-9037-7
Stroud, B. (2002). Explaining the Quest and Its Prospects: Reply to Boghossian and Byrne. Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition, 108(1/2), 239–247. Retrieved from https://www.jstor.org/stable/pdf/4321251.pdf
Stroud, B. (2004a). Précis ofThe Quest for Reality*. Philosophy and Phenomenological Research, 68(2), 384–386. https://doi.org/10.1111/j.1933-1592.2004.tb00349.x
Stroud, B. (2004b). Précis ofThe Quest for Reality*. Philosophy and Phenomenological Research, 68(2), 384–386. https://doi.org/10.1111/j.1933-1592.2004.tb00349.x
Stroud, B. (2014). Concepts of
Colour and Limits of Understanding. Retrieved July 1, 2019, from Philpapers.org
website: https://philpapers.org/rec/STRCOC-4
Page 198.
Stroud, B. (2018). Concepts of Colour and Limits of Understanding. In Seeing, Knowing, Understanding (pp. 193–205). Retrieved from https://books.google.nl/books?id=YhJbDwAAQBAJ&pg=PA193&lpg=PA193&dq=concepts+of+ colour+and+limits+of+understanding+barry+stroud&source=bl&ots=suFWIV2sNF&sig=ACfU3U0slRjEHRg6bQ8KvaZDg6ba8rvIKA&hl=nl&sa=X&ved=2ahUKEwilmqvigY7jAhWFblAKHYf8A9kQ6AEwAnoECAkQAQ#v=onepage&q=concepts%20of%20 colour%20and%20limits%20of%20understanding%20barry%20stroud&f=false
Stroud, B. (2019). The Significance of Philosophical Scepticism. Retrieved July 1, 2019, from Oup.com website: https://global.oup.com/academic/product/the-significance-of-philosophical-scepticism-9780198247616
Wikipedia Contributors. (2009, March 15). Colour charge. Retrieved from Wikipedia website: https://en.wikipedia.org/wiki/ colour_charge
Wright, W. (n.d.). Forthcoming in Philosophy of Science Review of Mazviita Chirimuuta’s Outside colour. Retrieved from http://www.mindstuff.net/ReviewOutside colour_WTW.pdf
Special thanks to Emma Young