Perception and the Physical World

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Reply Thu 8 Nov, 2007 12:15 pm
The doctrine of realism is a common sense doctrine which postulates at least two things:

1) The things in the physical world that we see and touch (or perceive in any other way) also exist when they are not being seen or touched or perceived. That is, things continue to exist in the same way even when we are not immediately aware of the things.

2)"in" objects which themselves appear to be coloured in different ways, considering that the apparent colour of things varies with conditions of illumination as well as organic conditions (consider "jaundice", for example)?

The questions some philosphers have asked are: do we ever truly see a "physical penny" in itself at all? Do we ever really see a "physical stick" in itself at all?


So, what would a completely objective view of physical objects (a 'god's eye' view) look like? Can we have a true perception of objects?

The philosopher John Locke has maintaied that since qualties such as colour and temperature are dependent upon the subjective observer then physical objects do not posess these qualities of colour and temperature. He states that since physical objects in themselves (i.e. when they are not being perceived) have neither colour nor temperature, then what we perceive are ideas (sense data, or percepts) and not the physical objects themselves.

And whether or not our ideas (our sense data) of physical objects are said to actually correspond to those objects, they are, claims Locke, seperate and distinct from the physical objects. Locke is saying that what we perceive in our sense data is not the same as what real objects posess. Locke's theory is called representational realism also known as The Veil of Perception.

It was Kant who said that we can know nothing of things as they are in themselves. He said that we cannot have knowledge of things as they exists when we are not perceiving them. Kant says that we can only know the 'appearances' of things which he called 'phenomena". Kant says that since an object is distinguished by the time under which it is observed and the space in which the act of observations takes place, then the true nature of an object must exist only by abstracting the object from time and space, which is impossible for man to do.

Kant says that humans 'create' the categories of time and space and thereby falsify objects; since the true nature of the object in itself is bound up with universal causation. To perceive an object then is to falsely 'remove' it or seperate it from its millenial cosmic path of becoming in time and its necessary supporting materials in space.
 
kennethamy
 
Reply Thu 8 Nov, 2007 01:27 pm
@Pythagorean,
Pythagorean wrote:
The doctrine of realism is a common sense doctrine which postulates at least two things:



2)


I just wonder who these naive realists are. I don't think that when I am on top of a tall building, that the people I see below me are as small as ants, although they look that small. And I don't think that a when I see a stick half-way immersed in water, that it really is a bent stick. And I don't think that when I see an object in near-darkness, that is doesn't have a color. And I don't know anyone who does. Do you? Everyone I know, except maybe for little babies, make adjustments for the conditions under which they perceive objects.
 
Fido
 
Reply Thu 8 Nov, 2007 02:11 pm
@Pythagorean,
The first part of the definition of realists suggests the principal of identity and conservation. The second part is just naive. Sure, we perceive things as they seem until we know better, but then we perceive with our minds where knowledge overrules appearance.

Locke is right that objects do not have color. Light has colors. Trees are green because they absorb all bandwidths except green, which they find useless. What we enjoy about living vegitation is vegitable trash. The same is true of temperature. Objects absorb heat, and radiate heat, but few are warm on their own unless their nature is a state of chemical reaction, as in rotting vegitation.

Kant is right in most respects. Wrong about space and time. We do not create them, but rather give them meaning. They are both non existent unless we perceive that to be understood, all things must exist in the context of time and space. To 'Know' something is to be able to place it in its context, to classify it both in time and space, and also as to catagory. The concept, or the idea, or the form represent reality as knowledge. And all concepts are conserved qualities that take for granted that nothing changes within our sight or out of our sight without another force acting upon it. It would be impossible for anyone to learn without some notion of conservation. Not even a child believes that when his mother is out of the room that she becomes something other, and when his mother returns he does not presume it is one of an infinite number of identical mothers waiting outside his door. Actual knowledge rests upon relatively few conserved qualities, but time changes all, or more correctly, all change in time, which gives time a constant reference in all things like the seasons which are cyclical.
 
Pythagorean
 
Reply Thu 8 Nov, 2007 04:41 pm
@Fido,
Fido,

Excellent post! Thank you for pointing out especially that most things do not generate their own source of heat. That was an astute observation on your part and one which I was not even thinking about.

Excellent analysis but what about time as viewed from a longer term, more cosmological perspective. It takes so many millions of years for a galaxy to form, for example. I was wondering what happens to your analysis of time and conservation if we were to look at the surface of the earth replacing minutes and hours with centuries? In this case the conserved ideas, forms or concepts are replaced with processes or matrices of ebb and flow. Maybe man must become more detached from the immediate world of nature in order to make the best objective evaluations?

But I think, if I am not mistaken, that is exactly what Kant is saying: The human understanding interferes with the processes of nature in order to procure for himself some knowledge. By giving local meanings (as you say), to time and space we disturb the inherent relations of the objects of knowledge whose relations are naturally intertwined and connected within broader cosmological considerations of causation which we do not have access to as yet. But perhaps there is a perspective that is possible that is outside of time? A perspective which knows the fundamental laws of physical reality and can 'see itself seeing itself' which can take the subjective aspects of time and space measurement into consideration and objectify everything including the observer himself? Maybe we can classify things without time?

I mean, we can't say we know one link in a chain because the one link has been artifically seperated from the great chain of being by us; but maybe if we went deep into the wilderness for example and sat down and meditated and forgot about the ego for a while and became part of the wilderness itself, then maybe we wouldn't be artifically seperate. This is something that I have been considering.

So I don't think you have proven to me that Kant was wrong by saying that we create time and space but you have surely enriched my thinking on the matter! You have further inspired me, Fido to think this through even more elaborately!

--Pyth
 
Pythagorean
 
Reply Thu 8 Nov, 2007 04:42 pm
@kennethamy,
kenneth,

Common sense realism i.e. naive realism is simply an unreflective, un-philosophical acceptance of the physical world as it appears to primitive men the nature of which is superficiality.

Is the shape of the penny circular or is it elliptical? OF course under a microscope a penny is neither circular nor elliptical but all across in every direction is rather bumpy like holey mountain ranges!
 
kennethamy
 
Reply Thu 8 Nov, 2007 06:43 pm
@Fido,
Fido wrote:
T

Locke is right that objects do not have color. Light has colors. Trees are green because they absorb all bandwidths except green, which they find useless.



But I don't understand why that shows that objects have no color. What that is explains why objects have color. After all, not only are objects green because of the explanation you give, but also, because human beings have the perceptual faculties that they have. To say that a leaf is green is to say that under normal perceptual conditions, the normal observer will see a green leaf. That does not mean that leaves are not green. Rather it tells us what it means to say that a leaf is green. You don't want to say that when leaves are seen at night when there is no light that leaves are no longer green, do you?

Locke did not say that leaves are not green. He said that color is a secondary property. That is very different.
 
kennethamy
 
Reply Thu 8 Nov, 2007 06:51 pm
@Pythagorean,
Pythagorean wrote:
kenneth,

Common sense realism i.e. naive realism is simply an unreflective, un-philosophical acceptance of the physical world as it appears to primitive men the nature of which is superficiality.

Is the shape of the penny circular or is it elliptical? OF course under a microscope a penny is neither circular nor elliptical but all across in every direction is rather bumpy like holey mountain ranges!


Pennies are circular, obviously. You seem to be assuming that unless a penny always appears to have the shape it actually has under all conditions of perception it has no shape. But that is absurd. The penny does have a shape. And it is the shape it appears to have under normal conditions of perception. Namely circular. The fact that a penny looks bumpy etc. has nothing to do with its shape. It can be bumpy, and still circular. Circular object may still be bumpy. The moon is quite bumpy. But it is accurate to describe it as circular, as contrasted (say) with triangular, or trapezoidal. Circular in shape does not mean, circular with no bumps.
 
Fido
 
Reply Thu 8 Nov, 2007 07:25 pm
@kennethamy,
kennethamy wrote:
But I don't understand why that shows that objects have no color. What that is explains why objects have color. After all, not only are objects green because of the explanation you give, but also, because human beings have the perceptual faculties that they have. To say that a leaf is green is to say that under normal perceptual conditions, the normal observer will see a green leaf. That does not mean that leaves are not green. Rather it tells us what it means to say that a leaf is green. You don't want to say that when leaves are seen at night when there is no light that leaves are no longer green, do you?

Locke did not say that leaves are not green. He said that color is a secondary property. That is very different.


Color is a property of light, and not of things. Matter absorbs radiation, and what we see is what it cannot absorb. If it is a property of anything it is of the chemical structures in the matter. It is just easier to say a thing is green than to say why it appears green. It is not green, but its green color is a negative quality. Am I correct in saying that the colors it absorbs reflect its chemistry but the colors it reflects does not since many things appear green for different reason, that is, not the same chemical makeup? I do not know if it is true in either case. Things are green which appear green, but its greeness tells us very little after all. Emiting of light at a certain bandwidth is an atomic property, of bosons I believe. Colors do tell us something of atomic structure.

I think your point is wrong about things being green because of perception. First of all, it is not a tree falling in the forest. It reflects light when is gets light. But the light it reflects has an essential relationship to the light it absorbs. A plant does not see as we see, but in the sense that it follows the sun, uses all it can of the energy of the sun and then emits not only the most useless color to it, but to all other plants, and shades those beneith, in that sense I can say it sees light as well as us. It is not perception that makes things real, but our perception that gives them meaning. If there were no humans to sense time, space, color, or any other attribute of reality, it would still be there; but it would have no meaning. Life gives all reality meaning.
 
kennethamy
 
Reply Thu 8 Nov, 2007 07:34 pm
@Fido,
Fido wrote:
Color is a property of light, and not of things. Matter absorbs radiation, and what we see is what it cannot absorb. If it is a property of anything it is of the chemical structures in the matter. It is just easier to say a thing is green than to say why it appears green. It is not green, but its green color is a negative quality. Am I correct in saying that the colors it absorbs reflect its chemistry but the colors it reflects does not since many things appear green for different reason, that is, not the same chemical makeup? I do not know if it is true in either case. Things are green which appear green, but its greeness tells us very little after all. Emiting of light at a certain bandwidth is an atomic property, of bosons I believe. Colors do tell us something of atomic structure.

I think your point is wrong about things being green because of perception. First of all, it is not a tree falling in the forest. It reflects light when is gets light. But the light it reflects has an essential relationship to the light it absorbs. A plant does not see as we see, but in the sense that it follows the sun, uses all it can of the energy of the sun and then emits not only the most useless color to it, but to all other plants, and shades those beneith, in that sense I can say it sees light as well as us. It is not perception that makes things real, but our perception that gives them meaning. If there were no humans to sense time, space, color, or any other attribute of reality, it would still be there; but it would have no meaning. Life gives all reality meaning.


Do you really mean that leaves are not green in the summertime? I didn't say they were "green because of perception". In fact, I don't really know what that means. I said that they were green, and that what was meant by saying that leaves are green is that leaves appear green to the normal observer under normal conditions. So, to say that leaves have some mass is not to say that leaves appear to have weight to the normal observer under normal conditions, but (to repeat) to say that leaves are green is to say that they appear green to the normal observer under normal conditions. So we are distinguishing between two different kinds of property of leaves: secondary, and primary. But John Locke never said that objects have not color. What he did was to explain how it is that objects have color.
 
Fido
 
Reply Thu 8 Nov, 2007 07:35 pm
@kennethamy,
kennethamy wrote:
Pennies are circular, obviously. You seem to be assuming that unless a penny always appears to have the shape it actually has under all conditions of perception it has no shape. But that is absurd. The penny does have a shape. And it is the shape it appears to have under normal conditions of perception. Namely circular. The fact that a penny looks bumpy etc. has nothing to do with its shape. It can be bumpy, and still circular. Circular object may still be bumpy. The moon is quite bumpy. But it is accurate to describe it as circular, as contrasted (say) with triangular, or trapezoidal. Circular in shape does not mean, circular with no bumps.


Part of the difficulty lies as always with the truth, which is how we fairly represent reality. If you are using a descriptor, what is it good for? My example for this is quite common: The uterus is a pear shaped organ. So what is a pear? A uterus shaped fruit? There is nothing like the other except the earth, which is slightly pear shaped. Or is that uterus shaped? We try to tell the truth about reality. We should try to understand that knowledge color perception. When we know why reality seems as it does we see reality in a different light. And perspective colors perception. Not one thing on this earth will ever apppear the same to two people.
 
kennethamy
 
Reply Thu 8 Nov, 2007 07:39 pm
@Fido,
Fido wrote:
Part of the difficulty lies as always with the truth, which is how we fairly represent reality. If you are using a descriptor, what is it good for? My example for this is quite common: The uterus is a pear shaped organ. So what is a pear? A uterus shaped fruit? There is nothing like the other except the earth, which is slightly pear shaped. Or is that uterus shaped? We try to tell the truth about reality. We should try to understand that knowledge color perception. When we know why reality seems as it does we see reality in a different light. And perspective colors perception. Not one thing on this earth will ever apppear the same to two people.



What has all that to do with the issue? The question is whether pennies are circular. The answer is yes, even if they do not appear circular under all perceptual conditions. The reason is that an object need not appear to have the shape it has under all conditions of perception. It would be interesting to ask why such a requirement has been imposed.
 
Fido
 
Reply Thu 8 Nov, 2007 07:52 pm
@kennethamy,
kennethamy wrote:
Do you really mean that leaves are not green in the summertime? I didn't say they were "green because of perception". In fact, I don't really know what that means. I said that they were green, and that what was meant by saying that leaves are green is that leaves appear green to the normal observer under normal conditions. So, to say that leaves have some mass is not to say that leaves appear to have weight to the normal observer under normal conditions, but (to repeat) to say that leaves are green is to say that they appear green to the normal observer under normal conditions. So we are distinguishing between two different kinds of property of leaves: secondary, and primary. But John Locke never said that objects have not color. What he did was to explain how it is that objects have color.


What leaf is has everything to do with the colors it absorbs and reflects, but it it is what it is, which is simply a leaf, and the color it reflects is green. Color is a quality of light, and the color an object reflects and absorbs is a characteristic of matter. Reflecting light is what it does, and is not what it is.
 
Fido
 
Reply Thu 8 Nov, 2007 07:58 pm
@kennethamy,
kennethamy wrote:
What has all that to do with the issue? The question is whether pennies are circular. The answer is yes, even if they do not appear circular under all perceptual conditions. The reason is that an object need not appear to have the shape it has under all conditions of perception. It would be interesting to ask why such a requirement has been imposed.


Pattern recognition is the key to our intelligence. Facial recogniton is essential for survival, or awarness of moods on a face. But this also extends to time. Since pennies and seasons are circular, though said cyclical, it also is percieved as a pattern. That is why what a thing appears to be is a requirement.
 
kennethamy
 
Reply Thu 8 Nov, 2007 08:49 pm
@Fido,
Fido wrote:
Pattern recognition is the key to our intelligence. Facial recogniton is essential for survival, or awarness of moods on a face. But this also extends to time. Since pennies and seasons are circular, though said cyclical, it also is percieved as a pattern. That is why what a thing appears to be is a requirement.



But it is not a requirement. No one thinks that any object has to appear the way it actually is in all circumstances. You don't, for example, think that an object looked at from a distance, must look the same size it does when you are near it, do you. That requirement, that an object must look the way it is through all conditions seems to have been imposed by philosophers. It is not a requirement of commonsense. As a matter of fact, if something looked the same under all conditions, we would suspect there was some trick going on. If a green object still looked green in the dusk, we would think that some artificial light was playing on the object, for objects do not normally look their real color when looked at in the dusk. A stick, half immersed in water may look bent (sort of, but not really, since it does not look the way a bent stick looks-not at all), but anyone who is above the age of 7 knows that the object is not really bent, however it may look like a bent stick.

I think these are all philosophical stories that are fed to us, and which no one who not has read them, even begins to believe. They just contradict the facts. Sticks half immersed in water simply do not look like bent sticks. Do they? And we expect objects to look different under different conditions of perception, without that meaning that some appearances are not their real appearances.
 
Fido
 
Reply Thu 8 Nov, 2007 09:47 pm
@kennethamy,
kennethamy wrote:
But it is not a requirement. No one thinks that any object has to appear the way it actually is in all circumstances. You don't, for example, think that an object looked at from a distance, must look the same size it does when you are near it, do you. That requirement, that an object must look the way it is through all conditions seems to have been imposed by philosophers. It is not a requirement of commonsense. As a matter of fact, if something looked the same under all conditions, we would suspect there was some trick going on. If a green object still looked green in the dusk, we would think that some artificial light was playing on the object, for objects do not normally look their real color when looked at in the dusk. A stick, half immersed in water may look bent (sort of, but not really, since it does not look the way a bent stick looks-not at all), but anyone who is above the age of 7 knows that the object is not really bent, however it may look like a bent stick.

I think these are all philosophical stories that are fed to us, and which no one who not has read them, even begins to believe. They just contradict the facts. Sticks half immersed in water simply do not look like bent sticks. Do they? And we expect objects to look different under different conditions of perception, without that meaning that some appearances are not their real appearances.


The fact that things look the same out of our sight, beyond our sight, and before we see them is essential to all rational understanding. It has a name, and it is a philosophical concept, but also a reality. In logic it is called identity, and in physics it is called conservation. All concepts represent conserved qualities. If they did not remain the same we could not recognize them, and could not name them. The difference between isolated phenomenon and examples of concepts is that they reoccur with the same attributes as before. In order to campare one example of a concept with another example of a concept the concept must remain unchanged. If you say one line is shorter than another you are able to compare them because each is conserved as a line, and the concept of line is conserved throughout. This means, for the purposes of philosophy that we are not comparing apples with oranges, but even more that we are not comparing one meaningless experience of a phenomenon with another just as meaningless.

We are able to recognize things as what they are by classification, that is by concept, such as 'leaf', or 'tree'. Everyone recogizes that thing change their appearance with distance or light; but they also recognize that they do not change their character with the circumstances. If we see a reed that appears as two reeds or as a sharply bent reed because of refraction, we do not need a concept to explain it to recognize that it is the same reed. Primitves fishing hit their mark with their spears because experience taught them where the fish was even without a scientific explaination.

In ever instance mind corrects for perception. We know the tree is green even in the dark. We only see it in the light, as it is the light we see. If the intellect could not distinguish one thing from another based upon experience we would be as blind as though we had no eyes at all. It is with imagination that we recogize things, but we do not verify with imagination. I can't even say that learning involves only one sense or the other. Rather, we see what we feel, and if it looks good we taste it. Some times that results in death, and everyone learns a lesson. So, we perceive withour minds and verify with our senses.
 
kennethamy
 
Reply Thu 8 Nov, 2007 11:46 pm
@Fido,
Fido wrote:
The fact that things look the same out of our sight, beyond our sight, and before we see them is essential to all rational understanding. It has a name, and it is a philosophical concept, but also a reality. In logic it is called identity, and in physics it is called conservation. All concepts represent conserved qualities. If they did not remain the same we could not recognize them, and could not name them. The difference between isolated phenomenon and examples of concepts is that they reoccur with the same attributes as before. In order to campare one example of a concept with another example of a concept the concept must remain unchanged. If you say one line is shorter than another you are able to compare them because each is conserved as a line, and the concept of line is conserved throughout. This means, for the purposes of philosophy that we are not comparing apples with oranges, but even more that we are not comparing one meaningless experience of a phenomenon with another just as meaningless.

We are able to recognize things as what they are by classification, that is by concept, such as 'leaf', or 'tree'. Everyone recogizes that thing change their appearance with distance or light; but they also recognize that they do not change their character with the circumstances. If we see a reed that appears as two reeds or as a sharply bent reed because of refraction, we do not need a concept to explain it to recognize that it is the same reed. Primitves fishing hit their mark with their spears because experience taught them where the fish was even without a scientific explaination.

In ever instance mind corrects for perception. We know the tree is green even in the dark. We only see it in the light, as it is the light we see. If the intellect could not distinguish one thing from another based upon experience we would be as blind as though we had no eyes at all. It is with imagination that we recogize things, but we do not verify with imagination. I can't even say that learning involves only one sense or the other. Rather, we see what we feel, and if it looks good we taste it. Some times that results in death, and everyone learns a lesson. So, we perceive withour minds and verify with our senses.


And what am I supposed to conclude from all of this? Is the leaf green or is it not. And do objects have real shapes that we observe or not? (I was under the impression that you said that leaves had no color. Now you say that (trees) leaves are green in the dark. Which is it?
 
Fido
 
Reply Fri 9 Nov, 2007 07:04 am
@kennethamy,
kennethamy wrote:
And what am I supposed to conclude from all of this? Is the leaf green or is it not. And do objects have real shapes that we observe or not? (I was under the impression that you said that leaves had no color. Now you say that (trees) leaves are green in the dark. Which is it?


The appearance of a leaf remains the same whether we see it or not. It is not perception that makes things real. We percieve much that is real with knowing where to look. We learn to distinguish between phenomenon, and mostly because they do not change. We do not affect the reality of things; but their meaning. And yes, leaves look green, but appear green because of what the plant is, because of a thing essential to the leaf, clorophil, which absorbs much of light energy but reflects green light. What a thing is in its underlying molecular or atomic structure is the why of its absorbing or reflecting light. The color found in white light that is reflected by an element is an attribute, a characteristic, or a quality of most things. So yes, I think it is entirely appropriate to say a leaf is green whether or not one understands that it is light that is green or any other color since the color a thing absorbs or reflects has a direct correlation with what it is. It is not its appearance that give it its reality, but its reality which give it an appearance. Things do not cease to be real because we no longer sense them, but they do lose their meaning when we can no longer sense them, as when we die.

Look. Something which may help here is something I learned about English in the process of trying to learn French. It is that the two most essential verbs in both languages are to have and to be, Avoir and Etre in French. And you will find in life that you are judged as often or as well on what you have in neglect of what you are. Some times these verbs are practically interchangeable. You can say: I have to go, or I am going. We say we are a certain age, and the French say they have a certain age. The two verbs are used to conjugate the other verbs. In the case of a leaf you can as well say it is green, or it has a green color.

What a leaf is, is why it is green in appearance. But things are not only their underlying structure, but all of the attributes that result from that structure. In the case of the leaf it is a reasonable conclusion that the structure followed from the energy it uses so that the light it rejects is essentially related to what it is. It is not arbitrary like a coat of paint, nor is it much useful since almost all leaves are green. I realize I am perhaps clouding the issue for you with every attempt to clarify. It is true that Color is a characteristic of visible light. If I say a tree is green, that is true of its appearance. If I say a tree is everything but green it is true to the facts because its primary source of energy, stored in carbon compounds that make up the tree, is from light waves which are not green.
 
kennethamy
 
Reply Fri 9 Nov, 2007 09:12 am
@Fido,
Fido wrote:
The appearance of a leaf remains the same whether we see it or not. It is not perception that makes things real. We percieve much that is real with knowing where to look. We learn to distinguish between phenomenon, and mostly because they do not change. We do not affect the reality of things; but their meaning. And yes, leaves look green, but appear green because of what the plant is, because of a thing essential to the leaf, clorophil, which absorbs much of light energy but reflects green light. What a thing is in its underlying molecular or atomic structure is the why of its absorbing or reflecting light. The color found in white light that is reflected by an element is an attribute, a characteristic, or a quality of most things. So yes, I think it is entirely appropriate to say a leaf is green whether or not one understands that it is light that is green or any other color since the color a thing absorbs or reflects has a direct correlation with what it is. It is not its appearance that give it its reality, but its reality which give it an appearance. Things do not cease to be real because we no longer sense them, but they do lose their meaning when we can no longer sense them, as when we die.

Look. Something which may help here is something I learned about English in the process of trying to learn French. It is that the two most essential verbs in both languages are to have and to be, Avoir and Etre in French. And you will find in life that you are judged as often or as well on what you have in neglect of what you are. Some times these verbs are practically interchangeable. You can say: I have to go, or I am going. We say we are a certain age, and the French say they have a certain age. The two verbs are used to conjugate the other verbs. In the case of a leaf you can as well say it is green, or it has a green color.

What a leaf is, is why it is green in appearance. But things are not only their underlying structure, but all of the attributes that result from that structure. In the case of the leaf it is a reasonable conclusion that the structure followed from the energy it uses so that the light it rejects is essentially related to what it is. It is not arbitrary like a coat of paint, nor is it much useful since almost all leaves are green. I realize I am perhaps clouding the issue for you with every attempt to clarify. It is true that Color is a characteristic of visible light. If I say a tree is green, that is true of its appearance. If I say a tree is everything but green it is true to the facts because its primary source of energy, stored in carbon compounds that make up the tree, is from light waves which are not green.


The appearance of a leaf remains the same whether we see it or not.

I don't understand the above sentence. You mean that a leaf looks green even in the dark? That seems to me to be contradictory. The leaf doesn't look to have any color in the dark. And, if the leaf is not seen, then the leaf does not look green. But a leaf can be said to be green in the dark, and to be green when it is not seen. So, if you mean to say that the leaf looks green in the dark, that seems to me contradictory. And if you mean to say that the leaf is green in the dark, I agree with you, but I thought that you denied that. So you will have to tell me whether you are contradicting yourself, or whether you have changed your mind.

I think that a leaf is green in the dark, and when it is not seen, because I analyze the sentence, "the leaf is green" as follows: "the leaf looks green to the normal observer in normal conditions". And, even when the leaf is in the dark, or when the leaf is not seen, it is true of it that the leaf (would) look green to the normal observer in normal conditions.

It is true that what you write is "cloudy", and it is not helpful that it is so prolix. (Part of the reason for this is that you try to explain why the leaf looks green. I don't think that is necessary. I think you can take it for granted that educated people know about the physiology of the perception of color). It seems to me that the essence of what can be said about this, can be said quite briefly. That is what I have tried to do.
 
Fido
 
Reply Fri 9 Nov, 2007 10:56 am
@kennethamy,
kennethamy wrote:
The appearance of a leaf remains the same whether we see it or not.

I don't understand the above sentence. You mean that a leaf looks green even in the dark? That seems to me to be contradictory. The leaf doesn't look to have any color in the dark. And, if the leaf is not seen, then the leaf does not look green. But a leaf can be said to be green in the dark, and to be green when it is not seen. So, if you mean to say that the leaf looks green in the dark, that seems to me contradictory. And if you mean to say that the leaf is green in the dark, I agree with you, but I thought that you denied that. So you will have to tell me whether you are contradicting yourself, or whether you have changed your mind.

I think that a leaf is green in the dark, and when it is not seen, because I analyze the sentence, "the leaf is green" as follows: "the leaf looks green to the normal observer in normal conditions". And, even when the leaf is in the dark, or when the leaf is not seen, it is true of it that the leaf (would) look green to the normal observer in normal conditions.

It is true that what you write is "cloudy", and it is not helpful that it is so prolix. (Part of the reason for this is that you try to explain why the leaf looks green. I don't think that is necessary. I think you can take it for granted that educated people know about the physiology of the perception of color). It seems to me that the essence of what can be said about this, can be said quite briefly. That is what I have tried to do.



It is wrong in a sense to say a leaf 'is' green. What a leaf is is why it is green. So color is secondary, and not primary to the matter of the leaf, as I believe Locke was saying. Either the color is green or the leaf appears green. But in deference to humanity which would say it is green because it reflects green light it is green. If you can't see it in the dark to know that it is green, shine a light on it and you will find it appears green.

Things are not real only because we perceive them. There are plenty of colorless, and oderless gasses to prove that we can be killed by what we cannot perceive. And it is not necessary to have a measurable, tangible quantity of justice or social equality to know they exist. Sense is the first step into a more scientific investigation. Yet there are things presumend by some to exist without the slightest real evidence that they do, like God, or Ether. But if people try to measure ether and come up with a zero they are likely to disregard it all together.
 
Fido
 
Reply Fri 9 Nov, 2007 11:59 am
@Pythagorean,
Pythagorean wrote:
The doctrine of realism is a common sense doctrine which postulates at least two things:

1) The things in the physical world that we see and touch (or perceive in any other way) also exist when they are not being seen or touched or perceived. That is, things continue to exist in the same way even when we are not immediately aware of the things.

2)


In fact a penny possesses each quality. It is not the single percepts by which it is recognized, but by the sum, essentially by all its qualities, which are physical, and can be measured. And the first statement is true.
Quote:


Also a stick when part of it is held under clear water appears bent. When we look at the stick in water are we looking at the real stick?

And also the same volume of water under certain conditions can feel cold to one hand and warm to the other hand.

Furthermore, how can colour be a quality "in" objects which themselves appear to be coloured in different ways, considering that the apparent colour of things varies with conditions of illumination as well as organic conditions (consider "jaundice", for example)?

The questions some philosphers have asked are: do we ever truly see a "physical penny" in itself at all? Do we ever really see a "physical stick" in itself at all?


So, what would a completely objective view of physical objects (a 'god's eye' view) look like? Can we have a true perception of objects?


We can have a true perception of objects. That is not to say a totally accurate perception of objects since all physical objects that can be sensed can be measured, but only assessed by sense. We get a relative sense of value from sense, but with science we seek a more absolute value.

Quote:


The philosopher John Locke has maintaied that since qualties such as colour and temperature are dependent upon the subjective observer then physical objects do not posess these qualities of colour and temperature. He states that since physical objects in themselves (i.e. when they are not being perceived) have neither colour nor temperature, then what we perceive are ideas (sense data, or percepts) and not the physical objects themselves.


We represent things through ideas but percieve things through qualities. As in the statement above those qualities are conserved even when out of our sight or else the whole fabric of reality folds up like a tent without poles.
Quote:

And whether or not our ideas (our sense data) of physical objects are said to actually correspond to those objects, they are, claims Locke, seperate and distinct from the physical objects. Locke is saying that what we perceive in our sense data is not the same as what real objects posess. Locke's theory is called representational realism also known as The Veil of Perception.


We can sense certain qualities of reality. What are we sensing? If we try to guess one thing , weight, we are measuring the attraction of an object to the planet. If we let the object fall, both earth and object fall together. Only when we objectively measure one thing against another as gold against aluminum do we get a true idea of weight. Yet, we can sense that much, that one thing weighs more than another; but when we come to think of it or talk about it, the difference must be represented in meaningful terms, which are ideas. Ideas, concepts, like weight, specific gravity, density are conserved qualities. We are sensitive, and reality can be sensed in many respects. What a thing is cannot be separated from those qualities we can sense. We cannot always say we sense every quality an object may be, but what we know is a result of what we sense.
Quote:

It was Kant who said that we can know nothing of things as they are in themselves. He said that we cannot have knowledge of things as they exists when we are not perceiving them. Kant says that we can only know the 'appearances' of things which he called 'phenomena". Kant says that since an object is distinguished by the time under which it is observed and the space in which the act of observations takes place, then the true nature of an object must exist only by abstracting the object from time and space, which is impossible for man to do.

We sense things by their appearance, phenomenon. From qualities we sense we can build up a notion of what it is. We catagorize that knowledge in the form of concepts. Kant might say we would have to sense things totally with our senses to say we can know anything about it, so that only finite knowledge is allowed to us. If he says that, I agree. If he is saying that a true nature is only an abstraction, he is correct; but only because the truth is an abstraction of reality. When we meet an object in reality it does not become less real because we cannot develop a 'true' idea of what it is. Reality is true to itself. Truth, if it is true, is true to reality. Nature, and reality is bigger than truth, which is a social concept. If we seem like the blind men and the elephant we can be forgiven for it is out of many truths that a full picture of reality can be concieved of.

Quote:

Kant says that humans 'create' the categories of time and space and thereby falsify objects; since the true nature of the object in itself is bound up with universal causation. To perceive an object then is to falsely 'remove' it or seperate it from its millenial cosmic path of becoming in time and its necessary supporting materials in space.


Time and space are both reality and concepts, ideas. Through them we give things perspective, before and after, near and far. If we can take an object mentally out of time and space we can examine it as though frozen. The reality is that all things are in flux, and not frozen. Yet, to learn more than we can perceive of an object in flux we must isolate it and freeze it. Is this true to nature? No. But it can help to build up a sense of truth, and the answers we arrive at can be true because truth is a representation of reality. The problem is this: it is impossible to work on a ticking clock or a beating heart. It is equally impossible to grasp the workings of the world while everything is in flux. Ideas, which are true to reality, are separate from reality, and are isolated bits of knowledge separate in time and space as nothing in reality ever is. Human knowledge is in the form of ideas. Reality, which we are a part of, is something we sense and perceive while we note our feelings. It is hardly exact, but considering that human knowledge is either entirely intuitive as when it considers social concepts; or scientific, when based upon qualities we first sense and then measure, it should not be discounted.
 
 

 
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