Quine on unactualized possibilia

I'd like to examine some arguments from Quine's On What There Is, one of the most famous papers in modern philosophy. In particular, I want to focus on Quine's comments concerning the Platonic riddle of nonbeing.

As Quine puts it: "Non-being must in some sense be, otherwise what is it that there is not?" In asserting, for instance, "Pegasus does not exist", I appear to commit myself to the existence, or to the being, of Pegasus. What is it that I'm saying doesn't exist? If Pegasus is nothing, then when we use the word "Pegasus", we're not talking about anything, which would render any statements containing the word nonsensical. "Pegasus does not exist" would amount to "_ does not exist". So, Pegasus, along with other nonexistent things, must have being of some sort, in order to account for the intelligibility of our discourse about nonexistents.

We might formalize the argument like so:

(P1) If "Pegasus" names nothing, then statements about Pegasus are nonsensical.
(P2) Statements about Pegasus are not nonsensical.
(C) So, "Pegasus" must name something.

Another way to see the problem is that it would appear that, if "Pegasus" and "Santa Claus" name nothing, than "Pegasus does not exist" and "Santa Claus does not exist" are each saying exactly the same thing. In each case, we're referring to nothing, and saying it doesn't exist.

(P3) If "Pegasus" names nothing and "Santa Claus" names nothing, then "Pegasus does not exist" and "Santa Claus does not exist" both say the same thing.
(P4) "Pegasus does not exist" and "Santa Claus does not exist" do not say the same thing.
(C) "Pegasus" and "Santa Claus" must each name something.

"Pegasus" names something, but what? One option is to hold that Pegasus has a kind of being as an unactualized possible object (Quine attributes this view to a character called "Wyman"). Reality consists of existent, actual objects; and also various nonexistent, merely possible objects.


Quine's objections to unactualized possibilia

1. First, how do we individuate such entities? What are their conditions of identity? The moment we try to analyze possible objects in any detail, we find that we can't answer simple questions about them:

Take, for instance, the possible fat man in that doorway, and, again, the possible bald man in that doorway. Are they the same possible man, or two possible men? How do we decide? How many possible men are there in that doorway? Are there more possible thin ones than fat ones? How many of them are alike? Or would their being alike make them one? Are no two possible things alike? Is this is the same as saying that it is impossible for two things to be alike? Or, finally, is the concept of identity simply inapplicable to unactualized possibles? But what sense can be found in talking of entities which cannot meaningfully be said to be identical with themselves and distinct from one another?

2. A second objection, related to the first, not explicitly stated by Quine but I think implicit in his paper, is that due to the problem of individuating possible objects, postulating possible objects doesn't actually solve the problem of referring to non-existent things. For if we can't individuate possible objects, we can't ever know what is being referred to when people use the term "Pegasus".

I don't think Wyman should be too troubled by these first two objections. In the first place, over the last few decades very detailed theories of modal metaphysics have been worked out that make answering questions such as these perfectly straightforward. Consider, for instance, Lewis's modal realism. Lewis would deny that there is a possible fat man in that doorway. Rather, at some possible world, a fat man is standing in the counterpart of that doorway. At some other possible world, a bald man is standing in the counterpart of that doorway. At some other world, a fat, bald man is standing in the counterpart of that doorway; at some other world, two fat, bald men are standing in the counterpart of that doorway; etc. Re whether any two possible men are alike, we evaluate the similarity of different possible objects in just the same way we evaluate the similarity of actual objects. Re identity, again, this is essentially just the same as for actual objects. (This is not to suggest that Lewis's theory, or any other realist theory of possibilia, is particularly plausible. But I think that Wyman could appeal to such developments to defuse Quine's objection.)

Second, as Richard Routley argues in his paper "On What There Isn't", precisely the same sort of difficulties arise for existing objects. Routley parodies the passage from Quine:

Take, for instance, the cloud in the sky above; and again, the adjacent cloud in the sky. Are they the same cloud or two clouds? How are we to decide? How many clouds are there in the sky? Are there more cumulus than nimbus? How many of them are alike? Or would their being alike make them one? ... is the concept of identity simply inapplicable to clouds? But what sense can be found in talking of entities which cannot meaningfully be said to be identical with themselves and distinct from one another?

Perhaps Routley isn't entirely fair here - surely there must be more difficulties with possible objects, if only because possible objects are so much more extensive, and include many stranger things, than actual ones - but the basic point is, I think, correct: just because it turns out to be difficult to answer seemingly simple questions about a certain class of objects, it hardly follows that we have reason to believe that there are no such objects. Reality is full of strange, difficult things. It's also full of perfectly straightforward things that turn out to be puzzling when subjected to certain questions, as when we try to come up with clear criteria for individuating clouds.

3. The notion of a possible object rests on a confusion. Modality, Quine suggests, applies to whole sentences, not to particular things. "It is possible there is a man in the doorway" is perfectly acceptable, the possibility in this case attaching to the sentence "there is a fat man in the doorway"; but it's illegitimate to infer from this to "there is a possible man in the doorway", with the possibility attaching to an entity, the fat man. (Quine doesn't present his reasoning for this in this paper. His arguments here are complex and I won't go into them here. I did start a video series on this, which I never got around to finishing. Michael Morris's An Introduction to Philosophy of Language also covers it.)

Quine suggests that the main motive for expanding possibility from sentences to objects is to deal with the riddle of nonbeing. I'm not convinced. I suspect that the main motive is the problem of explaining what the truthmakers of modal sentences are. The Nazis could have won WWII, I could have become a research chemist, nothing can exceed the speed of light, Frank couldn't have done any better in the exam, etc - in virtue of what, exactly, are such sentences true? Positing possible worlds is one way to deal with this.

4. Even putting aside the above problems, Wyman's account is simply incomplete. The postulation of unactualized possible objects doesn't help at all when we consider terms that apparently refer to impossible objects, such as "the round square cupola on Berkeley college". Quine suggests that one option for Wyman would be to hold that such terms are meaningless. So, regarding our riddle of nonbeing:

(P1) If "round square" names nothing, then statements about round squares are nonsensical.
(P2) Statements about round squares are not nonsensical.
(C) So, "round squares" must name something.

Wyman could reject (P2), accepting that "round square" names nothing and hence that statements about round squares are meaningless. Quine has two objections to this move. First, he argues, the claim that statements about round squares are meaningless "has no intrinsic appeal"; i.e. it's an unattractive and ad hoc hypothesis proposed simply to save the theory. Now, I'm not sure I agree with Quine here. To me, at any rate, "round square" does indeed seem to be meaningless, in some important sense. Of course, I can use the phrase "round square"; and I know what round things are and I know what square things are, so I might think that I'm able to make some inferences about what properties we might attribute to a round square. On the other hand, when I try to think about it in any detail, it slips out of my grasp. Can I really make inferences about it? Here's an easy one: it's a square, and square things have four sides, so it must have four sides. But this just ignores that we're talking about a round square. Round things don't have any sides.

It may be objected that "round square" is obviously contradictory, and this is why we struggle to assign any meaning to it. Sometimes however contradictions are disguised. Only on analysis do we realize that a proposed object is contradictory. Consider the suggestion that God, at least as conceived in Western monotheistic traditions, is contradictory, re arguments that properties such as omnipotence and omniscience lead to irresolvable paradoxes. Even if the atheist is correct about this, it's still the case that people have been able to talk about God in detail, and structure their lives around their belief in God, and even believe that they can have a personal relationship with God. Surely then we can't insist that the concept of God is simply meaningless.

There are two ways Wyman might deal with this. First, he could simply bite the bullet. Any concept that can be shown to entail contradictions is thereby meaningless. This is not such a radical position. The logical positivists held that a statement is meaningful only if it's analytically true or empirically verifiable; with this criterion they attempted to show that a whole host of apparently meaningful statements aren't meaningful after all, including statements about God (see e.g. Ayer's Language, Truth and Logic, chapter 6). Our ability to talk about God, to hold detailed religious beliefs, etc, can be explained by appealing to meaning in a weaker sense, e.g. emotional or poetic meaning. "Colourless green ideas sleep furiously" has no literal meaning, but we might say that it's meaningful in some extended, metaphorical sense.

Second, Wyman could reduce the force of the problem by suggesting that some contradictions are possible. Consider contradictory objects like the Penrose triangle or Penrose stairs.

Are these impossible? Round squares are simply inconceivable and can't be intelligibly talked about, but staircases that keep going up without ever getting higher can actually be visualized. By allowing that some contradictions are possible, Wyman significantly reduces the number of apparently meaningful statements he has to consign to meaninglessness. Of course, this option genuinely would be radical, but the ground has been prepared by dialetheism and paraconsistent logics.

Quine's second objection to the suggestion that statements apparently about impossible objects are meaningless is that this "makes it impossible, in principle, ever to devise an effective test of what is meaningful and what is not." Quine says: "it follows from a discovery in mathematical logic, due to Church, that there can be no generally applicable test of contradictoriness." I assume that what Quine actually has in mind is Gödel's second incompleteness theorem, which demonstrates, essentially, that any consistent formal system cannot prove its own consistency. So put simply: if contradictory objects are impossible, and statements about impossible objects are meaningless, then since there's no test for determining contradictoriness, there's no test for determining meaninglessness.

I have two comments about Quine's objection: (a) Why exactly do we need a strict, systematic way of determining what's meaningful? Why wouldn't it be good enough just to have a few basic rules of thumb? (It's not as though Quine is any stranger to indeterminacy of meaning!) (b) Again, Quine's criticism evaporates if Wyman severes the link between possibility and consistency, and holds that contradictory objects can be possible. Then he doesn't need to say that all contradictory statements are meaningless. In which case, it doesn't follow from the fact that there can be no effective test of what's contradictory that there can be no effective test of what's meaningful.

Ultimately then, it seems to me that rejecting (P2) is a much more plausible move than Quine suggests. Let me make one final comment here. Another obvious option for Wyman is simply to accept both (P1) and (P2), and draw the conclusion that there are unactualized impossibles, in just the same way as there are unactualized possibles. Quine objects to this move that if Wyman admits unactualized impossibles, then he will be trapped in contradictions. But why would this trouble Wyman? After all, he's openly admitting impossibles. Why wouldn't he also admit that some of those impossibles are contradictory?

5. Fifth, Quine suggests that the puzzle of nonbeing rests on a confusion between meaning and naming. Consider again (P1) and (P3):

(P1) If "Pegasus" names nothing, then statements about Pegasus are nonsensical.
(P3) If "Pegasus" names nothing and "Santa Claus" names nothing, then "Pegasus does not exist" and "Santa Claus does not exist" both say the same thing.

These claims seem to rest on the assumption that the meaning of a name is simply is referent (called direct reference theory or Millianism). If names have meanings above and beyond their referents, then "Pegasus" can be perfectly meaningful despite failing to refer to anything (and "Santa Claus" can also be perfectly meaningful, and can mean something different from "Pegasus", despite failing to refer). But Millianism has been subjected to a number of serious objections. Quine appeals to the famous problem of "Frege's Puzzle". Consider the following propositions:

(1) The Morning Star is the Morning Star.
(2) The Morning Star is the Evening Star.

"The Morning Star" and "the Evening Star" both refer to the same object, namely Venus, which on Millianism seems to entail that the phrases have exactly the same meaning. Now, if "the Morning Star" and "the Evening Star" have the same meaning, then we should be able to substitute one for the other in a sentence without changing the meaning of the sentence, which entails that (1) and (2) have the same meaning. But surely this isn't right: (1) is simply trivial, whereas (2) is interesting and informative; (1) is a tautology, whereas (2) tells us something important about the world; (1) is knowable a priori, whereas it takes hands-on empirical investigation to confirm the truth of (2).

I don't have anything to say about this point. I agree with Quine that Millianism isn't adequate, and that if Millianism goes, the justification for (P1) and (P3) is undermined.

6. Finally, Quine appeals to Occam's Razor. Admitting unactualized possible objects massively expands our ontology without good reason. Quine thinks there's an alternative, more ontologically parsimonious solution to the riddle, which appeals to Russell's theory of descriptions. I won't discuss Quine's own solution here. I only note here that the view that there exist, or there are are in some sense unactualized possibilia, has a variety of motivations (cf. Lewis again). Quine's appeal to Occam's Razor is rather less convincing if we have to accept possibilia anyway for other reasons.

Could we communicate with extraterrestrials?

Today I'm going to examine André Kukla's paper "One World, One Science", which is concerned with the question of whether, if we were ever to come into contact with an extraterrestrial civilization, we could learn to communicate with them. (Kukla calls this hypothetical alien race the "Aldebaranians"; I will follow him on this.)

The central worry about human-Aldebaranian communication is that their biology, culture, geography, developmental history, etc, will be radically different from ours, and this presents an obstacle to our ever developing an understanding of their language. How could we begin to learn the language of a society with which we share no common ground?

A popular response to this problem is what Kukla calls the "one world, one science argument" (OWOS). Whatever the differences between humans and Aldebaranians in culture, geography, biology, morality, etc, we both inhabit the same universe, and hence the basic laws of physics, chemistry and mathematics will be the same in both places. Hence, we can expect that human science and Aldebaranian science will have the same or at least similar content with respect to these areas. Kukla quotes Carl Sagan:

[H]ow could we possibly decode such a[n extraterrestrial] message? [...] The message will be based upon commonalities between the transmitting and receiving civilizations. Those commonalities are [...] what we truly share in common - the universe around us, science and mathematics.

To lay out the argument explicitly:

(1) OW: The laws of nature are the same everywhere. So:
(2) OS: Human science and Aldebaranian science will share at least some content, i.e. human science and Aldebaranian science will overlap.
(3) Finally, we conclude that this overlap will provide a common ground that will make communication possible.

Kukla first considers a couple of responses to OWOS that he doesn't develop. First, he notes that one response is to deny OW. In fact, humans and Aldebaranians don't share the same world; the laws of nature aren't the same everywhere. This response he attributes to those who hold extreme social constructivist views of science. Like Kukla, I don't find extreme social constructivism remotely plausible, though contra Kukla, it's not clear to me that social constructivists actually do deny OW. A more charitable interpretation of social constructivism is that it's just another way of denying OS.

Second, we can block the inference from OW to OS by appealing to conceptual relativism. As Kukla says, our science "depends not only on the nature of the mind-independent world, but also on the concepts and categories we employ for talking about the world." Notice that this is not to deny, as the social constructivists do, that science reveals facts about the world. Rather the point is that there may be many legitimate ways of describing the world, of "carving nature at its joints". The debate concerning different species concepts in biology is a good example of this; see my videos on the species problem (first; second). If the Aldebaranians don't share our concepts and categories, there's no reason why their science would be the same as ours, even if their science is also accurate. And why should we expect the Aldebaranians to have developed the same concepts and categories as us?

I'm not sure that this is really much of a problem. Other cultures conceptualize the world differently, yet this poses no significant threat to communication. See for instance Nisbett & Miyamoto's "The Influence of Culture": Western and Asian cultures perceive the world differently, with Westerners tending to perceive the world in an "atomistic" manner, viewing it as containing independent objects that are detachable from their context; and Asians perceiving it in a "holistic" manner, viewing objects as embedded in wider contexts and relationships. There is significant conceptual change over history; the ancient Greeks viewed the world in very different terms to us. We even find different conceptual schemes emerging in one and the same science: the example of different species concepts in biology has already been noted. In none of these cases do conceptual differences pose any problems to communicate. In general, humans are remarkably capable of adopting different conceptual schemes.

Of course, Kukla may object that for all we know, the concepts and categories possessed by the Aldebaranians would be radically different to our own, different to the extent that their overall science would be radically different - but then why should we believe that such radically different concepts would correctly describe the world? It's one thing to claim that two different conceptual schemes could both be accurate. Reflection on the many species concepts in biology confirms this. That two radically different conceptual schemes could both be accurate is a far stronger claim, and requires positive argumentation that Kukla doesn't provide.

There's another way to block the inference from OW to OS that Kukla doesn't discuss but is worth mentioning. At the very least, the move from OW to OS seems to require scientific realism: basically, the view that science correctly describes the world. We've already mentioned social constructivism, a particularly controversial alternative to realism. There are plenty of other alternatives.

Let's turn to Kukla's own arguments. He offers two arguments against OWOS: the selection problem and the superfluity problem. Most of his paper is concerned with the former.


The selection problem

Even granting OW, and granting that the Aldebaranians would have a similar conceptual scheme, Kukla thinks that the inference to OS fails. The problem is that neither of us will know all the scientific truths, and the scientific truths that we possess may not overlap with the scientific truths the Aldebaranians possess. Kukla dubs this the selection problem.

Is it acceptable to infer from OW to OS? Consider some proposition X that, if true, would falsify OS. At this point we have a mere logical possibility. (This of course means that OW doesn't logically entail OS, but nobody denies that.) The problem arises when we ask what probability to assign to X. The probability of X and the probability of OS are constrained with respect to each other. Putting it formally:

p(X) + p(OS) ≤ 1

The probability of X plus the probability of OS must be less than or equal to 1. It can't be the case that X is very likely and that OS is very likely. This point should be quite intuitive. X and OS are incompatible: if one is true, the other can't be true. So to say that X is very likely entails that OS is very unlikely. (Note: if X is false, this doesn't entail that OS is true. X's falsity simply places no constraints on the probability of OS. Even if X is false, OS might also be false for some other reason.)

X is the hypothesis that there is no overlap (or at least very, very little overlap) between human science and Aldebaranian science. If our sciences don't overlap, OS is false. So if X is likely, OS is unlikely. What, then, is the probability of X? Kukla suggests that we simply don't know. We have no good reasons for supposing that X is likely, and no good reasons for supposing that X is unlikely.

It follows that we also can't assign a probability to OS. Remember, p(X) + p(OS) ≤ 1. So if we assign a probability of e.g. 0.8 to OS, the probability of X can't be greater than 0.2. To be agnostic towards X means that we must be agnostic towards OS. And this means that the OWOS argument must be rejected. Now as Kukla points out, this isn't a decisive refutation. New evidence may arise that shows the probability of X to be low. This would put OS back on the rails. (Of course, new evidence might also show that the probability of X is high, which would refute OS decisively.) But it does show us that at present, we can't accept OS.

To summarize: Kukla's basic strategy against OWOS is to cite a proposition X that is inconsistent with OS and has an unknown probability. Since we must be agnostic about X's probability, and since X is incompatible with OS, we can't assign a high probability to OS (if OS has a high probability, this entails that X has a low probability, contradicting our agnosticism). Kukla's candidate for X is the proposition that human science and Aldebaranian science don't overlap.


Should we be agnostic about the probability of X? The defender of the OWOS argument will object that in fact, we have good reason to suppose that X has low probability. Kukla considers a number of such objections.

The fundamental laws solution: While we can't know all scientific truths, there are far fewer fundamental laws. So we can expect overlap on the fundamental laws. Kukla raises a number of objections: (A) Why should we believe there are fundamental laws? There might be no fundamental laws, but instead an infinite regress of laws, each explaining the other. A similar point here is that many philosophers tend to assume that there's a "bottom level" of reality, but perhaps it just goes on forever. Indeed, that would seem to be what induction on the past history of physics suggests; to quote Schaffer:

The history of science is a history of finding ever-deeper structure. We have gone from "the elements" to "the atoms" (etymology is revealing), to the subatomic electrons, protons, and neutrons, and now we are sometimes promised that these entities are really strings, while some hypothesize that the quarks are built out of preons (in order to explain why quarks come in families). Should one not expect the future to be like the past?

(B) Even if there are fundamental laws, there might be a huge number of them. (C) There's no reason to believe that we have attained the fundamental laws. Why assume that the Aldebaranians have?

I agree with Kukla that the fundamental laws argument doesn't work, but there's a very similar argument that he doesn't discuess and that I think has more potential. The argument rests on two claims. First, Aldebaranian science must, at the very least, deal with objects and processes on a scale that's also dealt with in our science. This follows from the fact that modern physics is applied at all scales: it deals not just with medium-sized objects, but also with the extremely large to the vanishingly small. Second, there is an objective structure to the world and science tracks this objective structure. This is a statement of a limited kind of scientific realism. The point here is that even if the goal of science isn't truth, in order for science to be successful enough to make accurate predictions and form the basis for technological development, in must in some ways latch onto how the world really is. (Aristotelian physics may have been wrong in many ways, but it wasn't completely wrong, and some of the claims of Aristotelian physics are preserved, or at least "imaged", in modern physics.) If these two claims are correct, we can expect some overlap between human and Aldebaranian science. This of course is only a sketch of an argument, but it provides a suggestion for how we might justify assigning a low probability to X.

The mathematics solution: Instead of appealing to science, the defender of OWOS might appeal to mathematics. We can expect humans and Aldebaranians to share mathematics, or at least certain parts of it. Elementary arithmetic, for instance, would surely be shared between two intelligent civilizations. However, Kukla objects that the selection problems applies to mathematics as well: there's no reason to think that there's any overlap in our mathematics. Even if we all have some mathematics, there's no reason to believe that we have the same mathematics.

I don't find Kukla's objection here very plausible. Bear in mind that humans have developed a great variety of mathematical systems, including extremely abstract ones and even inconsistent ones. We clearly have a very great flexibility with regard to the kinds of formal systems that we're able to understand and manipulate. Is it really plausible that the Aldebaranians use a form of mathematics that we could get no handle on? Indeed, that we could understand none of their mathematics and that they could understand none of our mathematics? Kukla thinks we must be agnostic about this since there's no evidence either way. But this strikes me as a fairly extraordinary claim, and hence one that demands some positive evidence. In fact, I think there might be some clear evidence against it. After all, any mathematics must involve patterns. We know how to distinguish between random noise and patterns, and we're also very good at decoding patterns.

The radio solution: If we can communicate with the Aldebaranians via radio, which appears to be the only option, they must at least have the ability to construct and use radio transceivers. We must share technology. Hence we must share some science. Kukla raises two objections to this: (A) He points out that no knowledge is required in order to develop radio communication; indeed, no intelligence whatsoever is required: organisms that perceive and emit radio transmissions could arise by natural selection. (B) More importantly, there's no reason to suppose that the Aldebaranians use radio.

The common conditions solution: This solution appeals to two hypotheses. First, "adaptive pressures instil a propensity to adopt certain ideas." In other words, natural selection has built in us innate tendencies to adopt certain beliefs about the world. If green berries are poisonous to us, it will promote survival and reproduction for us to be wary of green berries, for us to think that eating green berries is dangerous. Second, "there are conditions for survival that can be expected to obtain wherever intelligent life evolves." Kukla doesn't accept either of these hyptheses, but is prepared to grant them for the sake of argument (I will return to the latter hypothesis later). The defender of OWOS then argues as follows: Since both we and the Aldebaranians evolved in common conditions, we are likely to have faced similar evolutionary challenges. These similar challanges would have lead to similar solutions. In some cases, these solutions will take the form of certain true beliefs about the world. So, there are certain truths that both humans and Aldebaranians are likely to be innately disposed to accept. These truths are likely to be used in both human and Aldebaranian science.

This strikes me as an extremely silly, wildly speculative argument, leaping from premise to premise without any adequate justification. The appeal to common conditions can, I think, furnish a defense of the plausibility of human-Aldebaranian communication (again, I'll return to this later), but this particular defence is obviously inadequate. I won't deal with Kukla's discussion since I agree with him that argument doesn't work, and some of the problems are simply obvious. First, why believe that we face similar evolutionary challenges? Of course, at a very abstract level, all life forms must face similar challenges: how to find food, how to stay alive, etc. But at a finer grain, even species that evolve on in the same areas on the same planet don't share the same challenges; the lion doesn't face the same evolutionary challenges as the capybara. Second, why believe that similar challenges lead to similar solutions? Third, even if the argument is right that humans and Aldebaranians are innately disposed to accept the same beliefs about certain things, it's worth noting that the history of science is one of a constant violation of our intuitive beliefs. There's no reason to think that intuitive beliefs are likely to be preserved in scientific theories.


Finally, Kukla gives a transcendental argument for the selection problem: he argues that there's good reason to believe that the selection problem can't be solved; we can't ever show that X has a low probability. The reason is that we have no good reason to believe that the Aldebaranians have any science or mathematics whatsoever; and if they have no science or mathematics, a fortiori our science and mathematics have no overlap with theirs. All we know about the Aldebaranians is that they're intelligent beings. Intelligent beings need not have developed science and mathematics. Humans have always been intelligent, but we didn't develop science and mathematics until relatively recently.

Kukla is of course right about this. But I think defenders of the OWOS argument could argue that he's simply changing the subject. Is the only thing we know about the Aldebaranians that they're intelligent beings? No: we also know (because we've stipulated) that they've reached a high level of technological development. (Recall the passage from Sagan that Kukla quoted. We are to imagine a civilization that can transmit and receive interstellar messages. Of course, Kukla will point out, re his response to the "radio solution", that organisms need not have any technology or even intelligence to develop radio communication. While he's right that the basic elements of radio communication could arise by natural selection, reception and transmission of interstellar signals is another matter.) Surely nobody who's proposed the OWOS argument has in mind communication with extremely primitive extraterrestrials. Obviously "one world" doesn't entail "one science" if the extraterrestrials in question have no science whatsoever, just as "one world" doesn't entail "one science" if the extraterrestrials in question are merely simple microbes.


The superfluity of OWOS

Kukla's second objection to OWOS is that it's superfluous. Recall that the point of OWOS is to explain how we would be able to communicate with the Aldebaranians despite the apparent lack of any "common ground" between us. OWOS is supposed to show that actually, we do have common ground: namely in our basic science and mathematics. However, Kukla points out that we don't need to share any common ground in order to learn another person's language: "Babies do it all the time: they learn the language of beings with whom they share no prior topics of discussion, and they do it in a few years' time without expending any extraordinary effort." The correct response to the communication problem is not to demonstrate that we would share common ground with the Aldebaranians, but instead to reject that any common ground is required.

In a sense, of course, Kukla is right that babies don't share any "topics of discussion" with adults, just in virtue of the fact that babies aren't capable of discussing anything with adults. This however is completely trivial. In the same sense, the man who can only speak English shares no topics of discussion with a person who can only speak Japanese. So Kukla is just equivocating on the notion of "common ground". In the sense of "common ground" that people debating the OWOS argument are interested in - the sense that allows me to say that the English speaker shares a lot of common ground withh the Japanese speaker, but possibly no common ground with the Aldebaranian speaker - babies share substantial common ground with adults. They live in the same culture, they will experience the same geography, they have very similar biology, etc. They may even share a kind of innate "language module", as Chomsky has suggested with his theory of language acquisition.


Ultimately then, I think that Kukla's objections to OWOS are inconclusive. Before ending this post, I'd like to note a couple of points about the debate. First, one notable assumption by all parties in this debate is that communication would have to be linguistic. But why couldn't we, for instance, use pictures?

Second, defenders of OWOS grant that the only thing we could have in common is science and mathematics. I think this concedes too much to their opponents. Humans and Aldebaranians will probably have much more in common; I list three points. First, on any world, objects will have to move in much the same ways as they move on this one. The basic facts of mechanics and gravity are going to be same, no matter what world you live on. Second, there are strict limits on the kinds of chemistry that could be the basis for life, especially any life that could reach the complexity required for intelligence. Third, we can expect that humans and Aldebaranians will exhibit similar behaviours on a very abstract level. The Aldebaranians must have developed the capacity for experiencing something like pain, for instance, which will evince itself in withdrawal from harmful stimuli. Kukla is wrong to reject that we can expect common conditions for humans and Aldebaranians.

This is the real basis for the superfluity of the OWOS argument. In order to have good reason to believe that there's significant overlap between human science and Aldebaranian science, we must believe that there's some sort of overlap in the conditions in which we live. But this already provides the common ground needed for communication.