An argument against naturalism

This is another variant of Leon Porter's 1983 argument against semantic naturalism. Suppose:

1. Unless the reliability of our doxastic faculties can be explained scientifically, naturalism is false.
2. As a matter at least of nomic necessity, every grammatically correct sentence in the language of science (i.e., the language that a completed and correct science would use) expresses a proposition which is either true or false.
3. Only claims that can be made in the language of science can be given a scientific explanation.
4. If a language can express the claim that our doxastic faculties are reliable, then the language has a predicate T equivalent to (minimally: "of nomic necessity coextensive with") a truth predicate for utterances, and a predicate U equivalent to the predicate "is an utterance".
5. Some habitable locations in spacetime can be specified in the language of science solely in terms of relations to inorganic phenomena.
6. If x is any habitable location in spacetime that can be specified in the language of science solely in terms of relations to inorganic phenomena, and A and B are predicates in the language of science, then there is a nomically possible world at which there is a description D of x in the language of science, and an utterance at x of a sentence equivalent to "No item satisfying both A and B is located at any place satisfying D", with there being no other utterances at x.

Let's read some things off this. For a reductio, suppose naturalism is true. Then, from 1, 3 and 4 we learn that the language of science has "is true" and "is an utterance" predicates. From 5 and 6, we learn that an utterance of a scientific sentence equivalent to "No item that is both an utterance and true is located at any place satisfying D" nomically could be located at a place satisfying D, with no other utterances being located there. But such a sentence would be false if true and true if false, thereby contradicting 2. Hence naturalism is false.

I think the controversial claims are (1)-(3). Claim (1) is not a conceptual truth. But if the reliability of our doxastic faculties cannot in fact be explained scientifically, then naturalism fails to explains something that theism can explain easily and simply. Hence we have good reason to prefer theism to naturalism then. What makes naturalism in regard to us at all plausible is the possibility of evolutionarily explaining central features of us. But our doxastic reliability is one of those features.

Claim (2) is, perhaps, best seen this way. The language of all our modern scientific theories is such as to make (2) be true if these theories are true. It is extremely plausible that the same will be true of the language of completed science. If we think that the language of completed science will be mathematical, (2) is very plausible.

While (3) is plausible, one might worry a little about the conjunction of (1) and (2). One's worry might take this. Perhaps the explanation of our doxastic reliability is done in two steps. The first step is to philosophically establish a bridge between some scientific claim and the claim that our doxastic faculties are reliable, in such a way that one can argue philosophically that if the scientific claim is true, then our doxastic faculties are in fact reliable. I think this is only plausible, however, if the scientific claim includes predicates equivalent to "is true" and "is an utterance". (One might think that only the truth of beliefs, not of utterances, needs to be talked about scientifically. But I think this is mistaken in light of the way that language is in fact involved in our doxastic functioning.)

DIY

There is a special pleasure in making something oneself, something that works. For someone with my avaricious tendencies, a part of that pleasure is the pleasure of getting something for next to nothing. However, that is not everything, because a significant component in the pleasure is also there when one makes something for someone else. Moreover, some of the pleasure (though to me, a pleasure mixed with pain) would be present when one makes something even when one had to purchase tools and supplies that are more expensive than a commercial version of the item one is making.

There is also a special pleasure in using something one had made oneself. For instance, this summer I made myself a small blue 68mm refractor (for the pleasing price of about $17—$12 for a chipped lens, the chip being easily blacked out, $5 for miscellaneous hardware, and the rest being scrap like old cardboard tubes), which I normally use as a finder scope on my 13" Coulter (which I did not make), but which I also took along while visiting family, and put on my father's photo tripod. Even though the views through the small telescope weren't particularly impressive (though the dark skies of the B.C. Gulf Island where I was mainly using it helped!), there was a special pleasure in seeing distant galaxies through something I had made myself, a pleasure that would have been greater had I ground the objective lens myself and had I made the eyepieces myself.

The best explanation I know of these special pleasures of making and using something one had oneself made is that in both cases one is taking relish in a particular way in which we are in the image of God who is both creator and the self-sufficient one. (Another argument for the existence of God?)

Currently I am working on an 7.4" effective aperture Newtonian travel scope made from a cracked 8" mirror (some of it is duct-taped off) that I acquired for very little. So far I made the primary and secondary cells.

Of course the non-moral perfections involved—production and independence—are ones that are rather dangerous to us humans, especially independence which in fallen humans can be in tension with community and dependence on God, but of course as found in the blessed Trinity is in no tension with anything. There is the danger of vanity or even pride. (In the telescope-making, it helps to know that other people have done much better, and that my design has benefited from other people's experience and much advice from friends. Plus borrowing other people's tools--thanks, Trent!--makes it more of a communal project.)

Liar and Curry

Consider this sentence:

1. No true sentence (i.e., sentence that is true) satisfies F.

Observe that for some F's, this is quite unproblematic, and even true. For instance, no true sentence is written on the surface of Io, no true sentence is self-contradictory, no true sentence is such that it is both original and was uttered in the Honorable Member's speech. Now, if (1) is the one and only sentence that satisfies F, then (1) is a liar sentence. So some instances of (1) are paradoxical, and some are not.

In general, as in the Io case, it seems that:

2. When F does not have semantic vocabulary and no sentence satisfies F, then (1) is unproblematically true.

If we accept (2), we get an interesting result. Suppose that F is the predicate "is identical to (1) and not-p", where "p" is any non-semantic statement. Then, (1) says that no true sentence is identical to (1) and is such that not-p. This is equivalent to the claim that if (1) is true, then p. In other words, in this case, (1) is equivalent to a Curry sentence just like:

3. If (3) is true, then p.

Now suppose that p is in fact true. Then no sentence satisfies F, and by (2), it follows that (1) is unproblematically true. Therefore, it seems that (3) is also unproblematically true. But if (3) is unproblematically true, then we have established something quite interesting: Curry sentences with true non-semantic consequents are true.

No Curry sentence can be false. For if it's false, then it's true, because any material conditional with false antecedent is true. But whenever a Curry sentence is true, its consequent is true as well, by modus ponens (the antecedent is true because the Curry sentence is true!). So a Curry sentence is true when its consequent is true (assuming the consequent lacks semantic vocabulary) and is nonsense when its consequent is false.

Or so this argument shows. My own intuition is that (3) is nonsense even when p is true. But then I need to get out of the above arguments...

Sensory and religious experiences

One might think that the following marks a significant difference between religious and sensory experiences:

1. If x in context C has a veridical sensory experience of K, then typically another person in C with properly functioning sensory apparatus would also experience K.

Here, "context" does not include the fact of x's experiencing K, since then the conditional would be trivial. But, of course, (1) is not true in the case of religious experiences.

But (1) is false. Here is an easy counterexample. There are some things that are "on the edge" of normal human visual capabilities. For instance, seeing a paramecium or the Pinwheel Galaxy (in a dark enough sky) naked-eye is like that. If the organism were somewhat smaller or the galaxy somewhat fainter, people with normal vision would no longer be able to see it. But people with exceptional or well-trained vision (with "vision" understood broadly as including the brain post-processing of noisy data) still could. Thus there will be cases where a person has a veridical sensory experience of a tiny organism or a faint galaxy, but it is false that typically another person with properly functioning sensory apparatus would also see it. Only a person with exceptionally well functioning sensory apparatus would see it. Moreover, even such a person might not be able to see it under all conditions, but only under conditions of being optimally concentrated and rested.

Perhaps we can save (1) by replacing "properly functioning" with "properly functioning on this occasion at least as well as x's faculties in C were". Call this "(1*)". But now it is harder to tell that the analogue to (1*) is false in religious experience cases. For how would we compare how well different people's religious experience faculties are functioning on different occasions. So while it may be that the analogue to (1*) is false in religious experience cases, it is hard to give a non-theological argument for this. (One can give a theological argument by noting that God is surely free in choosing to whom he should reveal himself.)

Moreover, it seems that it can be a matter of chance what one sees and when. Last night, I was looking at NGC 6852 through my Coulter 13.1". Very faint, i.e., low contrast, even through an Oxygen III filter (it wouldn't have been so faint in a darker sky, but my backyard has a lot of light pollution). First, I just saw the blackness of the sky. Then eventually my eyes (or brain!) picked out a very, very faintly brighter patch of the darkness. Then that disappeared. It reappeared again. Eventually I managed to "hold it in view" for a longer time. A fuzzy elliptical patch of extremely faint light. It seems that I was dealing with a pretty random process of perception here: sometimes my brain was managing to pick the nebula out of the visual system noise and sometimes it wasn't. There may have been some oscillation in the atmosphere, but it probably wasn't relevant (it's relevant to seeing detail, but not so much to seeing a faint object).

Now, it is possible to put all this detail into the context C. But then one is in effect building into the context that the situation was such that one would manage to experience K. And that trivializes (1*) and makes it impossible to point out a difference with religious experience.

One might try to save (1) in a different way. Not by saying that the particular experiences—say, of that faint nebula—would be had by someone else, but by saying that anybody with properly functioning faculties at some point have some experience of this sort (say, a visual experience). But now it is not clear that religious experiences fail to pass muster. After all, a lot of people have religious-type experiences, say while seeing a sunset or a really elegant proof of the Pythagorean Theorem. And while some don't, it is far from obvious that this isn't just evidence that their sensus divinitatis is malfunctioning.

However, I think there is theological reason to think that this needn't just be a malfunction (e.g., think of the phenomenon of the dark night of the soul). So there is theological reason to think that religious experience is disanalogous in this way from sensory experience.

Death and the Second Coming

If I recall rightly, Aquinas had the somewhat strange idea that those people alive at the Second Coming would still die, though only for a moment (using "moment" non-technically). This is an odd position, and one might think it results from an overreading of Scriptural claims that all people die. But consider this argument:

1. (Consummated) Christian marriage only ends with death.
2. After the Last Judgment, there are no marriages.
3. All people will be alive after the Second Coming.
4. Therefore, all Christian married couples who are alive just before the time of the Second Coming will experience the death of at least one of the spouses by the time the Last Judgment is complete.

Now it seems like it would be really odd if God chose exactly one member of each married couple to die at the Second Coming. It would also be surprising if there were no Christian married couples alive just before the Second Coming (I suppose everyone might have become a monk or nun, but it seems improbable). So it is plausible that:

5. If (4), then all people on earth who are alive just before the Second Coming will die by the time the Last Judgment is complete.
6. Hence, all people on earth who are alive just before the Second Coming will die by the time the Last Judgment is complete.

One might challenge (1) as follows. Christian marriage ends with death or with the transformation of the body at the time of the general resurrection. We do not know what that transformation involves, but perhaps it is radical enough to make marriage no longer fitting.

Three dimensions of evaluation of bad actions

To steal pears without intending to sell or eat them is not only immoral, but hard to understand. To kill a rich and annoying uncle is easier to understand, but morally worse. And of course serial killers commit crimes that are both hard to understand and morally bad. The two dimensions, thus, appear to diverge.

Notice an interesting asymmetry between the morally good and the immoral. A morally good action may excite wonder, but it is not that hard to understand. It is only the immoral and the neutral action that can be really hard to understand.

A third dimension, which I indicated in an earlier post, is the degree to which the deed is reflective of a bad character. This dimension is to some degree independent of the preceding two. It is equally understandable why someone might kill for money or to defend a friend's honor in a duel, but the former reflects a more vicious character. Tormenting an invertebrate is less bad than killing to defend a friend's honor, but more reflective of a vicious character.

The dimensions are not entirely independent, however.

A variant of the genetic fallacy

Consider the following argument form:

1. p is believed because of argument A.
2. If A is a good argument, then q.
3. Not q.
4. Therefore, not p.

This is a kind of cross of the genetic fallacy with a denial of the antecedent (in the conditional: If A is a good argument, then p). For example:

5. The Immaculate Conception (the doctrine that Mary was saved by grace alone in the first moment of her existence) is believed because of the argument that Jesus would be subject to original sin if Mary was.
6. But if Mary's original sin would have infected Jesus, then the original sin of Mary's parents would have infected Mary, and so on, and hence all of Mary's ancestors would need to be without original sin.
7. But not all of Mary's ancestors are without original sin.
8. Therefore, the Immaculate Conception is false.

Notice, however, that there is an argument form in the vicinity of (1)-(4) that is better. Namely, we replace (4) with:

9. Therefore, the belief that p is not justified.

However, if we do that, we need to read (1) as saying "p is only believed because of argument A". But people are not very good at figuring out the reasons why they themselves believe something, and are much worse at figuring out why others believe something (that explains why so much political discussion is heated—for it is often difficult for people to figure out why someone might take a political position that disagrees with theirs, unless that person is stupid or vicious). So if the implied epistemic agent in (1) and (9) is someone other than the person offering the argument (1)-(3),(9), the argument is likely to be unsound in step (1). I think that when the argument form is found in the wild, it is common for (1) to fail.

Furthermore, it is important to keep constant the epistemic agent constant between (1) and (9).

I think the Marian case likely screws up on all of these counts. First of all, in (5) the epistemic agent is likely some ordinary believer or at best an incautious rookie apologist. In the analogue of (9), the epistemic agent is the Church. Second, even in the case of the ordinary believer or the rookie apologist, (5) ceases to be true if we read "is believed" as "is only believed", because in fact the ordinary believer and the apologist believe in the Immaculate Conception not just on the basis of their flawed argument, but primarily on the basis of the Church's authority.

Moreover, arguments of the form (1)-(3),(9) are often annoying to the interlocutors. I remember a job interview where a candidate tried to convince me that I only rejected his or her view because of thinking about a topic under the influence of a certain other position. This bit of mind-reading not only was incorrect (I can be accused of many things, but not of that particular influence; I rejected the candidate's view cause the conjunction of its claims obviously entailed some absurd proposition that we were both committed to the denial of), but I found it annoying and a bit offensive, and the other members of the interview committee did not like it either. That was a somewhat different version of the genetic fallacy, but the genetic fallacy is generally annoying.

There are places for arguments of the form (1)-(3),(9). But when one gives such arguments, danger is all about.

Circularity and regress

I am not entirely convinced of the arguments below. But they are fun.

Say that p is explanatorily prior to q provided that p contributes to some explanation of q. I shall assume that explanatory priority only holds between true propositions. Let us suppose that:

1. No contingent proposition is explanatorily prior to itself.

Thus, anybody who thinks that explanatory priority among contingent propositions could be circular—for instance, p prior to q, q prior to r, and r prior to p—is committed to denying the transitivity of explanatory priority.

Now, let us posit two plausible formal principles for explanatory priority:

2. If p is prior to q, and r is prior to s, then p&q is prior to q&s.
3. If p and q are conjunctions, and differ only in the order of the conjuncts, and p is prior to r, then q is prior to r.

For a reductio, suppose a circle of size three (the argument works in general): p is prior to q, q is prior to r and r is prior to p, where all three are contingent and true. Using (1) twice, we conclude that p&q&r is prior to q&r&p. Using (3), we conclude that q&r&p is prior to q&r&p, which contradicts (1), since the conjunction of contingent truths is a contingent truth.

Now suppose that a backwards infinite regress of contingently true propositions is possible:

4. ... p₋₃ prior to p₋₂, p₋₁ prior to p₀.

Then a doubly infinite regress is surely also possible:

5. ..., p₋₃ prior to p₋₂, p₋₁ prior to p₀, p₀ prior to p₁, p₁ prior to p₂, p₂ prior to p₃, ....

(Here is a quick way to go from (4) to (5): let p_n be the proposition that 1+1=3 or p_n−1 for n>0. Then, p_n−1 is explanatorily prior to p_n.) Suppose that all the propositions in the regress are distinct (otherwise, there is a circularity, which has already been ruled out). Suppose that the infinitary analog of (2) holds:

6. If A and B are two sets of propositions, with a one-to-one correspondence c between the members of A and those of B, such that c(a) is prior to a for every member a of A, and if p is the conjunction of all the members of A, and q is the conjunction of all the members of B, then q is prior to p.

Now, let A be the set of all the p_n for n an integer (positive, negative or zero). Let B=A. Let c(p_n)=p_n−1. The antecedents in (6) are satisfied. Hence, the conjunction of all the members of B is prior to the conjunction of all the members of A. But A=B. Thus, we have a violation of (1), once again.

The weakness of this argument is that (6) seems less plausible than the finite version (2).

An argument against (2) (and hence also against (6)) is that (2) implies that p can be prior to q even though p and q have a conjunct in common. (Suppose p is prior to q and q is prior to r; then p&q is prior to q&r.) And that might be implausible.

Conditionals

Imagine a language like English but that has no disjunction—it still, however, has conjunction and negation. There is a sense in which speakers of that language are not missing out on any aspect of reality. It may or may not be true that the English "p or q" expresses the same proposition as "it's not both the case that not p and that not q", but there seems to be an intuitive sense in which whatever reality is pointed out by "p or q", it is also pointed out by that disjunction-free circumlocution. Hold on to that sense of "not missing out".

Now, take a language like English but devoid of indicative and subjunctive conditionals. However, the language has disjunction, negation and conditional probabilities ("it is (very, somewhat, not at all, etc.) likely that ... given ..."). Are the speakers of that language missing out on any aspect of reality? Is there any irreducibly conditional aspect of reality?

Let me grant for the sake of argument that the English indicative "q if p" is not logically equivalent to "q or not p". But are there aspects of reality that can only be captured by indicative conditionals, with disjunction and negation not being adequate to the task? I do not know of any. That is a weak argument for their non-existence, I know. However, I tend to be fairly self-conscious about my use of conditionals, and I talk about a large variety of subjects, so there is some evidence here. Certainly, it does not appear that science requires an indicative conditional. "Either the reaction occurred or the chemicals were not mixed" seems to do just as well as "The reaction occurred if the chemicals were mixed."

There may be conditional obligations. But a conditional obligation either uses a sui generis conditional that is neither the indicative nor the subjunctive, or else can be expressed disjunctively: "Either I should do what I promised or I cannot reasonably do what I promised."

If Molinism is true, the subjunctive conditional is irreducible, and expresses features of reality that cannot be otherwise expressed. But I think Molinism is false.

It is tempting to think dispositions cannot be expressed in any way other than by subjunctive conditionals. But it's really hard to express dispositions even by means of subjunctive conditionals, given finkish problems.

Deep Thoughts XXII

The inevitable never fails to arrive.

The liar paradox and desire

The standard desire version of the liar paradox is to consider a person whose only desire is to have no satisfied desires. But that's a weird enough desire that one might wonder if it's possible to have it. Here is a version of the liar paradox using desires that are more imaginable.

Malefa has only one desire: That none of Bonnie's desires be satisfied. Bonnie has only one desire: That all of Malefa's desires be satisfied. Whose desire is satisfied? If Malefa's is, then Bonnie's isn't, and Malefa's isn't. If Malefa's isn't, then Bonnie's is, and Malefa's is, too.

What assumptions does this paradox depend on?

1. It is possible that Malefa and Bonnie both have the above desires.
2. The following disquotational schema for desire satisfaction is correct: A desire that p is satisfied iff I(p) (where I(p) is p rewritten with the subjunctive mood replaced by the indicative; thus, I("he eat ice cream") is "he eats ice cream"; to be more precise in the schema, I need to put in quotation marks of the right sort, but I'm not going to bother);
3. Classical logic.

In regard to (1), one might worry that it's not possible to have only one desire. But that's easily handled by modifying the cases. Maybe Malefa's strongest (or most intense or latest acquired) desire is that Bonnie's strongest (or most intense or latest acquired) desire not be satisfied, and Bonnie's strongest (or ...) desire is that Malefa's strongest (or ...) desire be satisfied.

Moreover, there is nothing absurd about having desires that someone else's desires be or not be satisfied.

One could do what I did in my Monday post and argue that whether Malefa actually manages to have the indicated desires depends on what Bonnie desires (or vice versa or both). Somehow, I find this less plausible in the case of desire—I guess I feel a pull of a certain internalism about desire.

A different move would be based on the Gorgias. In the Gorgias, Socrates argues at length that the tyrant, though he is able to put enemies to death and all that, gets less and less of what he wants the more powerful he is. The reason for that is that he does not really desire to put enemies to death and all that—what he really wants is happiness. There are a couple of ways of taking Socrates' point. One way is to say that there are no instrumental desires. If the tyrant had a desire to have enemies put to death, that would be merely instrumental. Another way (I think Heda Segvic took this view) is to make desire have a normative dimension, such that to desire is to desire appropriately, so that the tyrant does not desire the deaths of his enemies.

Both of these two readings undercut the view that everything that can be put in a (subjunctified) "that clause" can be an object of desire. Moreover, they in particular make questionable the possibility of one person desiring that another's desires not be satisfied: that desire seems too much akin to the tyrant's desire that so-and-so die.

The paradox gives support for the thesis of the Gorgias. But there is something uncomfortable in using a paradox to give support to a substantive philosophical position.

Moreover, one might think that the solution in the case of the desire-satisfaction form of the paradox should be the same as in the case of the truth form. I am not completely sure. (Here is a consideration to back up my uncertainty: the complements of desires are subjunctified that-clauses, while the complements of beliefs and assertions are indicative that-clauses. This observation weakens—ever so slightly—the standard view that the object of a desire is a proposition. But the object of belief and assertion is a proposition. (I say this without committing to a realism about propositions.))

An argument for semantic externalism

I am not actually convinced by this argument. But let's go.

1. If it is possible that whether an utterance expresses a proposition depends on what happens at the same time in distant places in the universe, then semantic externalism is true.
2. It is possible that whether an utterance expresses a proposition depends on what happens at the same time in distant places in the universe.
3. Therefore, semantic externalism is true.

I am not going to defend (1). It's fairly plausible, though I think it's actually a weak point. I want to defend (2). Suppose Fred and Janine are in distant places in the universe, and speak simultaneously. Fred says:

4. The sentence Janine is now uttering is true.

Janine says:

5. The sentence Fred is now uttering is not true.

It cannot be that both of Janine's and Fred's utterances succeed in expressing a proposition. For if they do, then if what Janine says is true, it is not true, and if what Janine says is not true, it is true, which is a contradiction. But in a world where Fred instead says:

6. 2+2=5.

and Janine still says (5), what Janine utters does express a proposition—indeed, a true one. And in a world where Fred still says (4) but Janine says (6), Fred's utterance expresses a false proposition. So it must be that whether Janine's utterance expresses a proposition depends on what Fred says far away, or that whether Fred's utterance expresses a proposition depends on what Janine says far away. Either option is sufficient to yield (1).

An optimistic B-theoretic way to think of finite lives

Thinking of the ever-decreasing amount of (earthly) life left can be depressing. That's the A-theoretic way. But there is a B-theoretic way: one can think of the span of one's life as a puzzle or painting that one needs to fill in in good ways. At any time t during one's life, one is only obligated to fill in the remaining parts of the puzzle or painting, the parts that are causally dependent on the here-and-now.

There is, in a sense, less stress the less of the puzzle or painting remains, since there is less of a future to make decisions for. Of course, one might have screwed up in the past, and now one has less time to compensate. But, apart from cases of genuine moral dilemmas, one is not obliged to do more than the best one can now do, and God's forgiveness is always available. The A-theorist can say many of the same things, but to me, these things fit better with the B-theory.

Take an extreme case. Suppose one is down to one minute left. Well, then, the problem is merely how best to live that minute. In a way, that is momentous, since it is a culminating minute. But, then again, it's only a minute, and unless one has a likelihood of deep wisdom, or sins that one hasn't repented of, the problem is not so great: the problem is merely how to live one minute.

At the same time, thinking of life in this way, as a puzzle or a painting to fill in, makes each moment crucial. For while a painter can always paint over a portion, we paint our lives in a way that does not allow for that. This is a way in which eternalist theories of time may lead to a cherishing of each moment, of living it out as best one can, since that moment always stands. A presentist can say similar things, but they seem less compelling then, I think.

The above is not an unattractive picture of life. Notice that there are two views here: one of life as a puzzle and the other as a painting. I think there is a way in which both views are right. Life is like a painting, but we are not the primary painter. The primary painter is God. For us, it is more like a puzzle, in that we should be trying to paint it in not according to our conception of what life is artistic, but according to God's. Moreover, we need not navel-gaze and puzzle-solve all that much, but all we need to do is love, and then God will take care of the painting (think of the life of a St Francis—here, there is a painting, but St Francis surely didn't care nearly as much about the painting, i.e., about his life, as about God, neighbor and the rest of creation). So there is a way in which the analogy isn't so good at all.

Ungrammatical sentences

I think there is something important to be learned in the philosophy of language from the fact that grammatically wrong sentences often succeed in clearly expressing propositions. (Maybe something along the lines of the claim that speaker meaning is the only meaning there is.)

Back in five minutes

You are visiting an office, and read: "I'll be back in five minutes." What have you been informed? Not that the person will return five minutes from now. Nor that the person will return five minutes from having written the note, since such notes can be re-used (this nicely shows that one can make an extended utterance simply by tacking up a sign—one is uttering, without writing, speaking or gesturing). Rather, you've been informed that the person returns five minutes from when the sign was made public.

You, obviously, understand the sign, and know what it says. What the sign says is, of course, the proposition which it expresses. So what does the sign say to you? It tells you, informs you, that the person returns five minutes from then, where of course the demonstrative "then" points to the time at which the sign was published. But that the person returns five minutes from then is a B-proposition. Hence, what the sign tells you is a B-proposition.

But unless we want to special-case posted signs, by exactly the same token when a person leaving an office tells you "I'll be back in five minutes", she is apprising you of a B-proposition, namely that she returns five minutes from then. It is simpler to handle the sign case and utterance case uniformly, so let's do that.

So now we see that paradigmatic A-sentences express B-propositions. But the A-theorist thinks that A-sentences express something other than B-propositions. Hence the A-theorist is wrong.

Objection: What you learn from the sign is the A-proposition that the person will be back five minutes from then.

Response: That is incorrect. Suppose that the sign was published at 1:30 pm, and you're reading the sign at 1:40 pm. The sign is informing you that the person is back five minutes from then, i.e., from 1:30 pm. But it is ungrammatical to say that you are informed that she will be back at t, when in fact t is in the past. (This is an interesting case of the phenomenon that whether a sentence is grammatically correct depends on non-linguistic facts. Another case would be the use of non-generic gendered pronouns.) Grammatically, what you would need to say is that she was back five minutes from then. But you can't say that if you don't know that the sign was published more than five minutes ago. So if you want to stick to tensed language, what you need to say is that she (in the generic sense of "she") was, is or will be back five minutes from then. That is, indeed, an A-sentence, but an eternal one. If all A-sentences express eternal A-propositions, then the the non-eternality in the A-theory is lost, and one might as well be a B-theorist.