“Cut the pie any way you like, 'meanings' just ain't in the head” -- Hilary Putnam

Although some may consider the subject one of less importance in the realm of philosophy. The debate between those who believe mental content to be purely an internal matter, and those who believe mental content to be dependent upon external factors has become a topic of interest for several philosophers in the late decades of the twentieth century. Those that believe mental content to be an entirely internal matter are collectively described as internalists. Such theorists will assert that to see what a mental state is about, we need to look no further than the internal properties of the mind. An externalist, in contrast, will insist that other properties external to the mind are necessary to determine what a mental state is is about. An important point to distinguish is that, when looking at internalism and externalism, we are looking at two theories of mental content, and not theories of mental causation; internalists and externalists may well be in complete agreement about what causes a mental state to occur. The debate over mental content, however, is a debate over what it is for a mental state to be about something, for a mental state to be about a rabbit, for instance, as opposed to a dog. In this debate, many find internalism to be the most intuitive view; in fact, some authors go so far as describe internalism as “most likely the commonsense view” (Goldberg & Pessin 106). Despite internalism's intuitive grasp, many strong arguments have been made for externalism in recent years. Perhaps the most notable of these arguments, originally “designed to establish semantic externalism,” is the Twin Earth argument, originally described by Hilary Putnam (Lau). Although Putnam's argument does an adequate job of pointing out several problems for internalism, another simpler and more revealing thought experiment may do the job of pointing out why the doctrine of internalism is not an acceptable model for mental content.

The most popular, and quite effective, example of why internalism ultimately falls short as a model for mental content comes from Hilary Putnam. In 1975, Putnam developed a thought experiment in which the reader is told to “imagine [. . .] there [is] a remote planet, Twin Earth, which [is] exactly like Earth except that instead of water [. . .] it [has] a different substance” (Lau). The different chemical substance is given the notation XYZ, and the substance is indistinguishable from water to everyone, at the macro level at least. If someone from Earth were to travel in a rocket to Twin Earth, they might use scientific equipment to observe that when people from Twin Earth say water they are actually talking about XYZ, and not H2O. In effect, we can say that the “word simply has two different meanings” (Putnam 10). When one says “water” on earth, they are referring to H2O; on Twin Earth, the word refers to XYZ. Putnam, however, for the purpose of the thought experiment, takes the reader back to a time when “chemistry was not developed on either Earth or Twin Earth” (Putnam 10). In effect, the chemical components of both substances on Earth and Twin Earth remain unknown, and there is no way to distinguish between H2O and XYZ. We can see the troubles an internalist model runs into when we contemplate the following situation. Suppose a person living on earth, who, following Putnam, we shall call Oscar, were to exclaim one day in 1975 that “water is beautiful.” Because Oscar has a twin on Twin Earth, which is exactly like the Earth we are all familiar with, Oscar's duplicate on the planet Twin Earth also makes the exact same exclamation regarding the beauty of water. Here is where we can see a problem with the internalist model, for although both Oscar and his counterpart are making the exact same statement, and have the exact same physical makeup, (we will ignore the fact that each twin has a different biological equivalent of “water”) their thoughts are about two different things. Oscar on Earth is making a statement about the chemical compound H2O, while the duplicate Oscar on Twin Earth is making a statement about the compound XYZ.

The preceding argument is strong, and well thought out, but it is not without its flaws. A problem present in Putnam's argument must be pointed out, although it is not one that we are unable to rectify with a slightly different thought experiment. Eddy Zemach points out that, in addition to H2O, there are other chemical compounds in existence that we refer to as water. Zemach concludes that “the extension of 'water' as used on Earth and Twin Earth is identical” (Zemach 62). Effectively, Zemach shows that the term water may apply to H2O, or XYZ. This is not the only criticism Putnam has received, however, and several critiques of Putnam's thought experiment can be made revolving around linguistic problems. Putnam makes a better case that is similar to his example of the chemicals H2O and XYZ; this example describes aluminum pots in contrast to molybdenum pots. The two types of pots are indistinguishable. Pots constructed on Earth are made out of what people on Earth call aluminum, and pots on Twin Earth are made out of what people on Earth call molybdenum. The catch is that “the words 'aluminum' and 'molybdenum' are switched on Twin Earth: 'aluminum' is the name of molybdenum and “molybdenum' is the name of aluminum” (Putnam 12). The reader should note that, although inhabitants of both planets are using the same words, what their statements are about are two different things. When a cook asks for an aluminum pot on Earth, and a Twin Earth cook performs the same action simultaneously, both cooks are referring to different compounds by the word “aluminum,” even though neither cook may have any conception of the chemical composition of aluminum. It should also be noted that this argument does not fall into linguistic problems as easily as the previous thought experiment; in this example we are talking about two different, yet very definite compounds.

Putnam takes the reader through one more example, which is a non-science fiction example. The example involves his own inability to distinguish “an elm from a beech tree” (Putnam 12). Putnam makes note that his concept “of an elm tree is exactly the same as [his] concept of a beech tree” (Putnam 12). He reasons that it would be illogical to suggest that his psychological state would be different when looking at a beech tree and calling it an elm, and despite the fact that he believes the two to be one in the same, what his perceptions would actually be about would be two different things. To extend Putnam's line of reasoning a bit, if he were to examine a beech and an elm in succession, and be unable to discriminate between any property at all in the two trees, it would illogical to suggest that his mental state was about the same thing upon perceiving the beech and the elm, despite an identical psychological state. Putnam goes on to suggest that, even if one were to suggest a conceptual difference between his extension of elm and his extension of beech, we could always support the point further by constructing a Twin Earth example with the words for elm and beech switched. This example, I believe is an improvement, but I would like to suggest a thought experiment that excludes the confusing and tangled-up baggage that comes with constructing two completely different planets.

The point that I would like to introduce will complement and hopefully improve on the arguments described by Putnam. Although Putnam's twin earth example does an appropriate job of providing us with a convincing case for externalism, there are other simpler thought experiments that we may do to give a clearer look at the problems an internalist will face, and clear up some of the difficulties that Putnam's example comes across. I would like for the reader to imagine a scenario that we will allow to take place with Charlie, an eager young philosophy student. One day, as this student is walking into class, a sinister doctor sneaks up on Charlie and injects him with a drug that will put Charlie to sleep for several days. While Charlie is completely unconscious, the brilliant and maniacal doctor constructs a perfect clone of the student. The doctor drags both of these pupils, who we shall refer to as Charlie A and Charlie B respectively, into separate, but indistinguishable rooms, and, with the utmost precision, he places each of the two in the exact same position on a small couch against one of the walls. The only actual difference between the two rooms, including the students in them, is that, in the center of one room, the room that Charlie A has been placed in, is a beautiful statue. In the room occupied by Charlie B is what seems to be a statue identical in appearance, but this statue is a hologram and does not exist physically in the same state as the statue in the room that Charlie A is in.

Both Charlie A and Charlie B are brought back to consciousness in exactly the same manner, and at precisely the same time. The mad doctor is monitoring everything that is going on in both rooms, including all of the neural activity that is going on in both student's brains. Because every detail of both Charlies is the exact same, right down to their neural operations, both of these two students have identical actions when they awake in their respective environments. The doctor speaks into a microphone which connects to a speaker set up in each room; simultaneously she asks both philosophy pupils to describe what they are seeing in the center of the room. Although both students are likely to be a bit disturbed about the unusual situation that they seem to be experiencing, we will assume that they are calm and collected enough to answer the question being addressed through the speaker. Both students, having the exact same histories, will describe the same object in the center of the room; perhaps they will discuss the artistic beauty of the statue, or maybe both Charlies will try to describe physical features of the statue. Both might say, for instance, that the statue is clearly made of granite. Despite the fact that what both of these philosophy students are perceiving and thinking is the same down to the last detail, what they are describing are two completely different things. In Charlie A's case, what is being described is, in fact, a large granite statue, whereas what Charlie B is describing is not a large granite statue, but a hologram constructed to look like a statue. The reader should note that, if the information regarding the state of the statues in the rooms was not available to the doctor directly, he would have no way of obtaining the data by viewing information internal to both Charlies. If, for instance, the mad doctor's husband were to come in and see all of the machines monitoring the internal happenings of both scholars, he would not be able to tell which scholar was having a mental state about the granite statue, and which student was having a mental state about the hologram. Information about the external environment is necessary.

Now suppose the internalist retorts by insisting that, although the external extension of what both students are thinking about is different, both mental states themselves are still about the same thing, that is, about a large granite statue. In other words, what both students are thinking about is a large granite statute, even though only one of the students has a large granite statue in front of them. The problem here is that, if this is true, both of their thoughts can still not be about the same thing; Charlie A is having thoughts about what is in front of him, and Charlie B is having thoughts about something that is not in front of him. Charlie B cannot be having a mental state about what is in front of them, and about a large granite statue; the two are mutually exclusive. Leibniz's law states that “if a and b are identical, then they must have all the same properties” (Goldberg & Pessin 42). The mental contents of both students cannot be identical, because it is impossible for these contents to share the same mental properties. We may say that Charlie B is thinking about a granite statue, but then he cannot be thinking about something in front of him, so either Charlie B is thinking about a large granite statue and is wrong about the assumption that there is one in front of him, or he is thinking about what is in front of him, and is wrong in his assumption that the object is a granite statue. Charlie A, on the other hand, can be thinking about what is in front of him, and a granite statue, as the two are one in the same. Exactly what Charlie B is thinking about I will leave open to debate, but it is clear that both student's mental content cannot be the same. The reader should note that this thought experiment does not fall into some of the more problematic traps that Putnam's Twin Earth argument does. The argument itself does not require any linguistics whatsoever, for neither Charlie A or Charlie B are required to say or think anything linguistically while in their two separate rooms. It is difficult to see how anyone could contest that a granite statue and a hologram of a granite statue are the same extension of the word “granite statue.” Both Charlies speak the same language and, indeed, have exactly the same history, yet what their thoughts and perceptions are about are completely different. Furthermore, any number of specific examples may be used ranging from the very simple, to the very complex. For instance, Charlie's professor may be introduced in one room, while an exact duplicate is released in the other room; Both Charlies have the same thoughts and perceptions, but only one of these students would behaving thoughts of an original professor standing in front of them.

Putnam's original thought experiment in support of externalism was a good example of why mental content is not only an internal matter, but the the example is not without its faults. In my own thought experiment, I have eliminated some of the problems that Putnam's Twin Earth example has faced while keeping the necessary elements that show support for externalism. In effect, we have a case where language arguments similar to the ones made by Zemach against Putnam's example are ineffective, so the internalist will have to focus on different arguments, which, if they can be made compelling, I believe will be more relevant to the actual debate anyway. I have given a simple, clear model that is in support of externalism; to overcome this case, the internalist will have to somehow show how two individuals with identical constitution are in the same mental state when what they are perceiving, and what their thoughts are actually about, are two entirely different things. Case in point, we can see that a simpler and more clear argument, which follows the same theme as Putnam's, presents several problems to the doctrine of internalism. The story of Charlie and the mad doctor is such a model, as it eliminates a lot of the language problems that externalists face.

Works Cited

Goldberg, Sanford, and Andrew Pessin. Gray Matters: An Introduction to the Philosophy of Mind. Armonk, NY: M. E. Sharpe, 1997. 104-120.

Lau, Joe, "Externalism About Mental Content", The Stanford Encyclopedia of Philosophy (Fall 2004 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/fall2004/entries/content-externalism/>.

Putnam, Hilary. "The Meaning of 'Meaning'." The Twin Earth Chronicles. Comp. Sanford Goldberg, and Andrew Pessin. Armonk, NY: M. E. Sharpe, 1996. 3-52.

Zemach, Eddy. "Putnam's Theory on the Reference of Substance Terms." The Twin Earth Chronicles. Comp. Sanford Goldberg, and Andrew Pessin. Armonk NY: M.E. Sharpe, 1996. 60-68.

Works Consulted

Dennet, Daniel C. Consciousness Explained. Boston: Little, Brown and Company, 1991.

Patterson, Sarah. "The Explanatory Role of Belief Ascriptions." Philosophical Studies 59 (1990): 313-332.

Tye, Michael. Externalism and Memory. The University of Texas at Austin. 24 Apr. 2005
<http://www.utexas.edu/cola/depts/philosophy/faculty/tye/Memory.html>.