Chapter VIIIa, “The Relation of Sense-Data to Physics,” pages 145-164
Russell breaks down Chapter VIII into twelve sections; the chapter is sufficiently involved that my summentary itself will be broken into two posts. This first post (part “a” of Chapter VIII) covers the following sections:
I. The Problem Stated (p. 145)
II. Characteristics of Sense-Data (p. 147)
III. Sensibilia (p. 148)
IV. Sense-Data are Physical (p. 150)
V. ‘Sensibilia’ and ‘Things’ (p. 152)
VI. Constructions versus Inferences (p. 155)
VII. Private Space and the Space of Perspectives (p. 158)
VIII. The Placing of ‘Things’ and ‘Sensibilia’ in Perspective Space (p. 162).
The follow-up post, part b of Chapter VIII, will cover the remaining sections:
IX. The Definition of Matter (p. 164)
X. Time (p. 167)
XI. The Persistence of Things and Matter (p. 169)
XII. Illusions, Hallucinations, and Dreams (p. 173).
Now equipped with that barebones (yet formidable) context, on to the summentary of Chapter VIII…
Physics employs the usual scientific method of experiment and observation. But what we ultimately observe is limited by our senses, and that sense data is not the atoms and molecules themselves. What we think we know about atoms is through suspected correlations with the sense data. But how could such correlations be verified, given that only one side of the correlation, the sense data, will ever be known to us?
We could try to solve the inference problem by postulating some a priori truths: this is the route that philosophy often takes. The postulate-a-truth solution goes beyond experiment and observation, of course, which makes it inadvisable. Alternatively, we could define objects like atoms “as functions of sense-data [p. 146].”
The way we talk about physics is somewhat backwards. We say that when a certain type of wave meets our eyes, that certain colors are perceived. “But the waves are in fact inferred from the colours, not vice versa [p. 146].” So physics goes beyond experimental evidence to the extent that the waves are not themselves defined as functions of the data. From “stuff implies data” we need to move to “data imply stuff.”
We receive multiple sense data at any point, so it isn’t obvious of what a single sense datum consists. For our purposes, we can even accept a complex fact (A is to the left of B), as a sort of sense datum, even though, as opposed to a proper sense datum, the complex fact could be false.
Sense data exist when they are data, but whether the stuff that is sense data persist before or after when they are data is uncertain. “Sense-data at the times when they are data are all that we directly and primitively know of the external world [p. 148].” But there can be more than we know. [We are sort of like flatlanders trying to grasp 3D objects – RBR.] Physics (like metaphysics) in some sense deals with all the particulars, known to us or not. But the physics that we know of needs must deal only with sense data.
“Sensibilia” are the stuff akin to sense data, but without being sensed by any mind. (“Sensibile” is the singular form.) Sensibilia become sense-data by entering into a relationship (of acquaintance with a mind), like men become husbands by entering into a marital relationship. Can we infer (directly unobserved) sensibilia from sense data?
Sense data form “part of the actual subject matter of physics [p. 149].” Even when they are unobserved sensibilia, they are subject matter: observing sensibilia (and hence making them sense-data) adds only awareness to that which is already present.
“Physics” is related to “physical,” and Russell takes “physical” to refer to the stuff that is the subject matter for physics [!?]. A particular is “mental” if it is itself aware of something; facts are “mental” if they involve mental particulars. Russell hopes to show that sense data are physical – they might also be mental, but that is neither here or there for present purposes. [Russell (p. 151) notes that he does not accept the “new realist” position of Mach and James, though Russell’s discussion here is consistent with that position.] Sometimes the questions of the persistence and the physicality of sense data are conflated. Russell will argue that the data are physical – and hence within the scope of physics – though they probably do not persist in an unchanged way.
“Logically a sense-datum is an object, a particular of which the subject is aware [p. 152]” – and the subject is not a part of the sense-datum. The existence and the persistence of sense-data (or proto sense-data) do not require, of necessity, a sensing subject. The subject has sensations, his or her awareness of sense-data, and sensations are mental objects – though sense-data are physical.
We know that a table or other sensibilia appear differently to different people. But can a table (or other sensibile) in the same place simultaneously be both brown (to one observer) and yellow (to another)? Russell cites an article (pdf here) by T. P. Nunn for explaining how this subjectivity does not render sensibilia to be non-physical. Nunn’s solution notes that there are two “places” in question, the place at which the table appears and the place from which the table appears. Each observer’s place at which the table appears is not comparable to that of any other observer – though there can be correlations between these separate spaces. “No place in the private world of one observer is identical with a place in the private world of another observer [p. 154].” A table, then, could be the class of all appearances, or potential appearances, sensibilia, of the object in question. Though the appearances are not identical and cannot exist in the same place at the same time, the table is no less a physical concept – and we don’t need to adopt some ideal realm that contains the actual table.
Mathematical logic has developed the method of replacing a sort of imagined or inferred concept (like irrational numbers) with a constructed concept. Dr. Whitehead is the pioneer, and he suggested the application to physics of this approach to me [Russell].
“A complete application of the method which substitutes constructions for inferences would exhibit matter wholly in terms of sense-data, and even, we may add, of the sense-data of a single person, since the sense-data of others cannot be known without some element of inference [p. 157].” But we are far from achieving this ideal. In the meantime, we can discipline those inferences which cannot be avoided: they should be general, explicit, and similar to that stuff whose existence is already given – on this last principle, Kant’s thing-in-itself fails.
Russell permits two inferences: the sense-data of other observers (which uses analogy to accept the existence of other minds, and which rules out building a solipsistic basis for physics); and, the sensibilia that lack a current observer.
No sensibile can be a sense-datum to two observers simultaneously – though their sense-data will be similar, and two people can speak meaningfully of the same table. Everyone has their own private world of sense-data, different from everyone else’s. The place at which a sense-datum exists is a private space. There is no issue, then, with an object having two appearances in the same place, as those appearances exist in separate, observer-specific spaces. Multiple appearances of an object are not an argument against the physicality of the object.
“In addition to the private spaces belonging to the private worlds of different percipients, there is, however, another space, in which one whole private world counts as a point, or at least as a spatial unit [p. 159].” This is the space of perspectives, and its points (individual perspectives) do not require an actual observer to be present making perceptions. Nearby perspectives contain closely correlated sensibilia, and these sensibilia correspond to appearances of one object. Indeed, the object itself can be defined as the class of its appearances.
We can order all the perspectives of a thing in a space by taking similar views – those in which a penny looks perfectly circular, for instance – and arranging them by apparent size. The spatial order we end up with would have been replicated with any object that possessed the same set of appearances (though we could use an ordering metric other than size). “It is this empirical fact which has made it possible to construct the one all-embracing space of physics [p. 161].”
We now have a six-dimensional world: a three-dimensional collection of perspectives, where each perspective is itself three-dimensional. An object has associated with it many lines of perspective, and where they meet is itself a perspective, the one where the object is, the place “at which” it appears. But each perspective also provides its own place “from which” the object appears. Psychology is interested in studying sensibilia in the “from which” place, and physics is interested in studying sensibilia in the “at which” place.
Observers can order the appearances of an object by their proximity (to the mind of the observer, say); “those are nearer which belong to perspectives that are nearer to ‘the place where the thing is [p. 163].’” The fact that, by squinting, the appearance of an object changes, when we tend to suspect that the object itself does not change, is no longer a problem for regarding objects as physical. A thing is a class of appearances. If some appearances change – by squinting, say – then there is some change in the object. But we can define change in an object as occurring only when appearances that become arbitrarily close to the object also change. Squinting results in a change in something, but not in the object perceived.
Russell breaks down Chapter VIII into twelve sections; the chapter is sufficiently involved that my summentary itself will be broken into two posts. This first post (part “a” of Chapter VIII) covers the following sections:
I. The Problem Stated (p. 145)
II. Characteristics of Sense-Data (p. 147)
III. Sensibilia (p. 148)
IV. Sense-Data are Physical (p. 150)
V. ‘Sensibilia’ and ‘Things’ (p. 152)
VI. Constructions versus Inferences (p. 155)
VII. Private Space and the Space of Perspectives (p. 158)
VIII. The Placing of ‘Things’ and ‘Sensibilia’ in Perspective Space (p. 162).
The follow-up post, part b of Chapter VIII, will cover the remaining sections:
IX. The Definition of Matter (p. 164)
X. Time (p. 167)
XI. The Persistence of Things and Matter (p. 169)
XII. Illusions, Hallucinations, and Dreams (p. 173).
Now equipped with that barebones (yet formidable) context, on to the summentary of Chapter VIII…
Physics employs the usual scientific method of experiment and observation. But what we ultimately observe is limited by our senses, and that sense data is not the atoms and molecules themselves. What we think we know about atoms is through suspected correlations with the sense data. But how could such correlations be verified, given that only one side of the correlation, the sense data, will ever be known to us?
We could try to solve the inference problem by postulating some a priori truths: this is the route that philosophy often takes. The postulate-a-truth solution goes beyond experiment and observation, of course, which makes it inadvisable. Alternatively, we could define objects like atoms “as functions of sense-data [p. 146].”
The way we talk about physics is somewhat backwards. We say that when a certain type of wave meets our eyes, that certain colors are perceived. “But the waves are in fact inferred from the colours, not vice versa [p. 146].” So physics goes beyond experimental evidence to the extent that the waves are not themselves defined as functions of the data. From “stuff implies data” we need to move to “data imply stuff.”
We receive multiple sense data at any point, so it isn’t obvious of what a single sense datum consists. For our purposes, we can even accept a complex fact (A is to the left of B), as a sort of sense datum, even though, as opposed to a proper sense datum, the complex fact could be false.
Sense data exist when they are data, but whether the stuff that is sense data persist before or after when they are data is uncertain. “Sense-data at the times when they are data are all that we directly and primitively know of the external world [p. 148].” But there can be more than we know. [We are sort of like flatlanders trying to grasp 3D objects – RBR.] Physics (like metaphysics) in some sense deals with all the particulars, known to us or not. But the physics that we know of needs must deal only with sense data.
“Sensibilia” are the stuff akin to sense data, but without being sensed by any mind. (“Sensibile” is the singular form.) Sensibilia become sense-data by entering into a relationship (of acquaintance with a mind), like men become husbands by entering into a marital relationship. Can we infer (directly unobserved) sensibilia from sense data?
Sense data form “part of the actual subject matter of physics [p. 149].” Even when they are unobserved sensibilia, they are subject matter: observing sensibilia (and hence making them sense-data) adds only awareness to that which is already present.
“Physics” is related to “physical,” and Russell takes “physical” to refer to the stuff that is the subject matter for physics [!?]. A particular is “mental” if it is itself aware of something; facts are “mental” if they involve mental particulars. Russell hopes to show that sense data are physical – they might also be mental, but that is neither here or there for present purposes. [Russell (p. 151) notes that he does not accept the “new realist” position of Mach and James, though Russell’s discussion here is consistent with that position.] Sometimes the questions of the persistence and the physicality of sense data are conflated. Russell will argue that the data are physical – and hence within the scope of physics – though they probably do not persist in an unchanged way.
“Logically a sense-datum is an object, a particular of which the subject is aware [p. 152]” – and the subject is not a part of the sense-datum. The existence and the persistence of sense-data (or proto sense-data) do not require, of necessity, a sensing subject. The subject has sensations, his or her awareness of sense-data, and sensations are mental objects – though sense-data are physical.
We know that a table or other sensibilia appear differently to different people. But can a table (or other sensibile) in the same place simultaneously be both brown (to one observer) and yellow (to another)? Russell cites an article (pdf here) by T. P. Nunn for explaining how this subjectivity does not render sensibilia to be non-physical. Nunn’s solution notes that there are two “places” in question, the place at which the table appears and the place from which the table appears. Each observer’s place at which the table appears is not comparable to that of any other observer – though there can be correlations between these separate spaces. “No place in the private world of one observer is identical with a place in the private world of another observer [p. 154].” A table, then, could be the class of all appearances, or potential appearances, sensibilia, of the object in question. Though the appearances are not identical and cannot exist in the same place at the same time, the table is no less a physical concept – and we don’t need to adopt some ideal realm that contains the actual table.
Mathematical logic has developed the method of replacing a sort of imagined or inferred concept (like irrational numbers) with a constructed concept. Dr. Whitehead is the pioneer, and he suggested the application to physics of this approach to me [Russell].
“A complete application of the method which substitutes constructions for inferences would exhibit matter wholly in terms of sense-data, and even, we may add, of the sense-data of a single person, since the sense-data of others cannot be known without some element of inference [p. 157].” But we are far from achieving this ideal. In the meantime, we can discipline those inferences which cannot be avoided: they should be general, explicit, and similar to that stuff whose existence is already given – on this last principle, Kant’s thing-in-itself fails.
Russell permits two inferences: the sense-data of other observers (which uses analogy to accept the existence of other minds, and which rules out building a solipsistic basis for physics); and, the sensibilia that lack a current observer.
No sensibile can be a sense-datum to two observers simultaneously – though their sense-data will be similar, and two people can speak meaningfully of the same table. Everyone has their own private world of sense-data, different from everyone else’s. The place at which a sense-datum exists is a private space. There is no issue, then, with an object having two appearances in the same place, as those appearances exist in separate, observer-specific spaces. Multiple appearances of an object are not an argument against the physicality of the object.
“In addition to the private spaces belonging to the private worlds of different percipients, there is, however, another space, in which one whole private world counts as a point, or at least as a spatial unit [p. 159].” This is the space of perspectives, and its points (individual perspectives) do not require an actual observer to be present making perceptions. Nearby perspectives contain closely correlated sensibilia, and these sensibilia correspond to appearances of one object. Indeed, the object itself can be defined as the class of its appearances.
We can order all the perspectives of a thing in a space by taking similar views – those in which a penny looks perfectly circular, for instance – and arranging them by apparent size. The spatial order we end up with would have been replicated with any object that possessed the same set of appearances (though we could use an ordering metric other than size). “It is this empirical fact which has made it possible to construct the one all-embracing space of physics [p. 161].”
We now have a six-dimensional world: a three-dimensional collection of perspectives, where each perspective is itself three-dimensional. An object has associated with it many lines of perspective, and where they meet is itself a perspective, the one where the object is, the place “at which” it appears. But each perspective also provides its own place “from which” the object appears. Psychology is interested in studying sensibilia in the “from which” place, and physics is interested in studying sensibilia in the “at which” place.
Observers can order the appearances of an object by their proximity (to the mind of the observer, say); “those are nearer which belong to perspectives that are nearer to ‘the place where the thing is [p. 163].’” The fact that, by squinting, the appearance of an object changes, when we tend to suspect that the object itself does not change, is no longer a problem for regarding objects as physical. A thing is a class of appearances. If some appearances change – by squinting, say – then there is some change in the object. But we can define change in an object as occurring only when appearances that become arbitrarily close to the object also change. Squinting results in a change in something, but not in the object perceived.
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