[4.2.8.] “The Common Sense View of the World.”

 

At this point Moore gives (2) a name: “the ‘Common Sense view of the world’.” (182) (I will abbreviate this “CSV”.)

 

And he makes the following points about it:

 

(a)               All philosophers actually accept CSV. The difference between Moore and some of those philosophers is that those philosophers hold views that are inconsistent with CSV. For example, as soon as a philosopher asserts that there are other philosophers, she reveals that she does in fact accept CSV. She might go on to assert that there are no physical objects, but in doing so she is contradicting herself (since philosophers have physical bodies).

 

(b)               Even to say that we know that a given proposition belongs to CSV is to commit oneself to the truth of CSV. Suppose that someone says that we know that the belief that physical objects exists is part of the CSV. What this implies is that we (we philosophers with human bodies, extended in space) exist. So “it is self-contradictory to maintain that we know them to be features in the Common Sense view, and that yet they are not true; since to say that we know this, is to say that they are true.” (182)

 

(c)                Setting aside any claims about what we know... There are some claims that belong to CSV of which it is the case that, if they belong to CSV, then they are true. Moore is not terribly clear on this point, but I think he has in mind the following: if there is such a thing as the CSV at all (whether or not we know about it), then there must be people who subscribe to it. So there are some claims, like

·         “There are human beings, who at different times have had different experiences” that must be true, given that there is such a thing as the CSV at all. If there were not human beings having different experiences at different times, there would be no such thing as the CSV!

 

 

[4.2.9.] Certainty vs. Ability to Analyze.[1]

 

Some early members of the tradition of analytic philosophy (especially Russell and the early Wittgenstein) engaged in philosophical analysis in a narrow sense of “analysis,” in which it means breaking something down into its smallest components.

 

In section IV of “A Defense of Common Sense,” Moore shows himself to be an analytic philosopher in this same narrow sense: he is concerned with analyzing specific common-sense propositions in an attempt to discover what they really mean.

 

Moore has argued that there are many “common sense” propositions about which we can be certain that they are true.

 

But he is very unsure regarding the analysis of such propositions. In other words, he believes that we can be certain that these common-sense propositions are true, even if we do not necessarily know how to analyze them correctly.

 

For example, he is not sure about the analysis of the proposition

 

“Material things have existed.”

 

We can be certain that this is a true proposition, but (says Moore) it is not clear how it is to be analyzed. How it should be analyzed depends on how some simpler, more fundamental propositions should be analyzed, propositions such as:

 

¯          “I am perceiving a human hand.”

“I am perceiving a pen.”

“I am perceiving a sheet of paper.”

etc.

 

But these propositions cannot be analyzed unless we know how to analyze even simpler, even more fundamental propositions, such as:

 

¯          “I am perceiving this.”

“This is a human hand.”

 

Analyzing this sort of proposition is very difficult—and an analysis of “Material things have existed” (and thus an understanding of the nature of material things themselves) depends on our ability to analyze such propositions.

 

(But again, we can be certain that material things have existed even if we cannot yet analyze that claim.)

 

[Cf. Carnap’s reductionism, according to which, e.g., the meaning of “x is an arthropod” can be gotten to by showing which primary sentences (a.k.a. observation sentences) it implies and which primary sentences imply it.]

 

 

[4.2.10.] Sense Data.

 

Moore says that he is certain of only two things about the analysis of such fundamental propositions as “I am perceiving this” and “This is a human hand.”

 

1.      For each such proposition, there is a sense datum that is a subject of the proposition—it is one of the things that the proposition is about.

 

2.      “[W]hat I am knowing or judging to be true about this sense-datum is not (in general) that it is itself a hand, or a dog, or the sun, etc., etc., as the case may be.” (183) In other words, the propositions are about sense data, but they are not saying that the sense data are the objects being perceived—they are saying something else.

 

To get what Moore means by “sense datum” (plural: “sense data”), he asks us each to look at our own right hands. By “sense datum” he means the thing

 

with regard to which [you] will see that it is, at first sight, a natural view to take that that thing is identical, not, indeed, with [your] whole right hand, but with that part of its surface which [you are] actually seeing, but will also (on a little reflection) be able to see that it is doubtful whether it can be identical with the part of the surface of [your hand] in question. Things of the sort (in a certain respect) of which this thing is, which [you] see[] in looking at [your] hand, and with regard to which [you] can understand how some philosophers should have supposed it to be the part of the surface of his hand which he is seeing, while others have supposed that it can’t be, are what I mean by ‘sense-data.’ (183)

 

So by “sense datum” Moore seems to mean whatever it is that we directly perceive when we perceive something with the senses. An example of a sense datum is that thing about which you might wonder, when looking at your right hand:

 

Question SD: “Is this thing of which I am having a visual experience a part of the surface of my hand itself?”

 

He does not assume that sense data are mental. He leaves open the question whether sense data are mental or are part of the material world (the world outside our minds). In other words, he is not presupposing an answer to Question SD.

 

For example, he leaves as an open question whether a sense datum of my hand is something mental (my experience of my hand) or whether it is actually part of the visible surface of my hand.

 

Now, in his attempt to analyze the proposition “This is a human hand,” Moore asks: what is it that we know, when we know that “this is a human hand?”

 

Well, what we know is not that this sense datum is a human hand, since obviously the sense datum (whether or not it is mental) is not an entire hand—at most it is a part of the visible surface of a hand.

 

Moore suggests the following as the correct analysis of “This is a human hand”:

 

¯          “There is a thing, and only one thing, of which it is true both that it is a human hand and that this surface is a part of its surface.” (183)

 

[Notice the Russellian nature of this analysis. Like a Russellian translation of a sentence containing a definite description, it contains an existence claim, a uniqueness claim, and a predication.]

 

 

[4.2.11.] Two Theories of Perception.

 

But now the question arises: how ought we to analyze this proposition about the sense datum?

 

Moore considers three possible analyses, all of which are (he says) problematic [we will consider only two of them]. Each analysis corresponds to a different theory of perception, a theory about what is going on when we perceive objects in the world. The modern names for these theories are direct realism and indirect realism (Moore does not use these names):

 

direct realism (df.): we directly perceive objects that are external to the mind, i.e., the immediate objects of perception are extra-mental (outside the mind); we do not perceive those objects by way of intermediaries (mental representations or ideas). This theory combines metaphysical and epistemological elements:

·         metaphysical: there exist objects external to the mind, independent of perception;

·         epistemological: we perceive those objects directly, rather than by perceiving some mental intermediaries.

 

indirect realism (df.): we indirectly perceive objects that are external to the mind, i.e., the immediate objects of perception are mental items that represent objects outside the mind. This theory combines metaphysical and epistemological elements:

·         metaphysical: there exist objects external to the mind, independent of perception;

·         epistemological: we perceive those objects indirectly, by perceiving some mental intermediaries.

 

 

[4.2.11.1.] Direct Realism

 

According to the first analysis, the sense datum is part of the surface of the hand; so when I know that this is part of the surface of the hand, I know that the sense datum itself is part of the hand’s surface.

 

If this is true, then what we perceive directly when we are looking at a hand (i.e., the sense datum) is part of the surface of the hand itself.

 

But according to Moore, there are two problems with direct realism...

 

Problem with Direct Realism #1.

 

If this view is true, then our sense data do not “always really have the qualities which they sensibly appear to us to have” (184).

 

For example, suppose I look at my hand, and then someone else looks at my hand through a microscope. One and the same surface will appear very different to each of us. And yet, if that surface is the sense datum we each see, we are each seeing one and the same sense datum.

 

So if the sense datum is the surface of the hand, and we are both seeing the surface of the hand, and the surface of the hand appears different to each of us, then one and the same sense datum must appear different to each of us.

 

It follows that sense data do not always have the characteristics they appear to have.

 

This is deeply mysterious, since (by definition) sense data are the things that we perceive directly… so how could they not be what they seem to us to be?

 

Moore thinks this is a problem for direct realism, but not a fatal one. He takes a second problem to be more important...

 

 

Problem with Direct Realism #2.

 

Sometimes we “see double,” i.e., we have (at the same time) different sense data of the same surface.

 

But if a sense datum of a surface is ever part of the surface itself, it is so in the case of seeing double; i.e., if in fact our visual sense data are parts of surfaces, the fact that on some occasion we happen to be seeing double does not change that fact.

 

But a sense datum cannot be part of the surface itself in the case of seeing double, since there are two different sense data and only one surface.

 

So sense data are never visible surfaces themselves.

 

This problem is a specific case of a traditional argument against direct realism: the argument from hallucination. Here is a contemporary statement of this argument, by Robert Audi:

 

1.       A perfectly faithful (visual) hallucination of a field is intrinsically indistinguishable from an ordinary experience of seeing that field, that is, not distinguishable from it just in itself as a visual experience, as opposed to being distinguishable through verifying one’s visual impression by touching the things around one. ...

2.       [Therefore, w]hat is directly seen, the immediate object of one’s visual experience, is the same sort of (non-physical) thing in a perfect hallucination of a field as in an ordinary experience of seeing a field. ...

3.       What is directly seen in a hallucination of a field is not a field (or any other physical thing).

4.       [Therefore, w]hat is directly seen in an ordinary experience of seeing a field is not a field.[2]

 

 

[4.2.11.2.] Indirect Realism.

 

Moore is still considering ways to analyze the following sentence about a sense datum: “There is a thing, and only one thing, of which it is true both that it is a human hand and that this surface is a part of its surface.” (183)

 

According to the second view he considers, the sense datum is not part of the surface of the hand; rather, the sense datum is something that stands in some relation “R” to the surface of the hand.

 

There are many different versions of this analysis, differing about what exactly the relation “R” is between the sense datum and the hand’s surface.

 

But, says Moore, the only plausible version is the one that holds that R is an unanalyzable relation of being an appearance of (or, in other words, being a manifestation of).

 

So what we know when we know that “This is a human hand” is: this sense datum is an appearance of part of the surface of a human hand.

 

But according to Moore, there is a big problem with indirect realism...

 

Problem with Indirect Realism:

 

If this view is true, then there is no way we could ever know that there is a human hand of which our sense datum is an appearance. If what we are immediately aware of is, not part of the hand itself, but merely the appearance or representation of the hand, then we are epistemically blocked—we can never know anything about the hand... or about any other material objects!

 

But Moore has already stated the common sense view that we can know for certain that material things (like hands) exist. So on his view, indirect realism cannot be right.

 

 

[Moore also considers a third theory of perception: a form of phenomenalism defended by John Stuart Mill. We will not consider what he says against that theory.]

 

 

In summary:

 

We all know a great many “common sense” beliefs to be certainly true.

 

But it is far from clear how to analyze many of these beliefs; in particular, questions about what it is that we directly perceive when we perceive a material object are far from settled.

 

 

Stopping point for Wednesday April 15. For next time, read all of Gettier’s “Is Justified True Belief Knowledge?” (pp.219-220 – it’s a very short article).