I think that the idea of ‘adding up to normality’ is incoherent, but maybe I don’t understand it. There is a rule of thumb that, in general, a theory or explanation should ‘save the phenomena’ as much as possible. But Egan’s law is presented in the sequences as something more strict than an exceptionable rule of thumb. I’m going to try to explain and formalize Egan’s law as I understand it so that once it’s been made clear, we can talk about how we would argue for it.
If a theory adds up to normality in the strict sense, then there are no true sentences in normal language which do not have true counterparts in a theory. Thus, if it is true to say that the apple is green, a theory which adds up to normality will contain a sentence which describes the same phenomenon as the normal language sentence, and is true (and false if the normal language sentence is false). For example: if an apple is green, then light of such and such wavelength is predominantly reflected from its surface while other visible wavelengths are predominantly absorbed. Let’s call this the Egan property of a theory. A theory would fail to add up to normality either if it denied the truth of true sentences in normal language (e.g. ‘the apple isn’t really green’) or if it could make nothing of the phenomenon of normal language at all (e.g. nothing really has color).
t has the property E = for all a in n, there is an α in t such that a if and only if α
t is a theoretical language and ‘α ‘is a sentence within it, n is the normal language and ‘a’ is a sentence within it. E is the Egan property. Now that we’ve defined the Egan property of a theory, we can move on to Egan’s law.
The way Egan’s law is articulated in the sequences, it seems to be an a priori necessary but insufficient condition on the truth of a theory. So it is necessary that, if a theory is true, it has the Egan property.
If α1, α2, α3..., then Et.
Or alternatively: If t is true, then Et.
That’s Egan’s law, so far as I understand it. Now, how do we argue for it? There’s an inviting, but I think troublesome Tarskian way to argue for Egan’s law. Tarski’s semantic definition of truth is such that some sentence β is true in language L if and only if b, where b is a sentence is a metalanguage. Following this, we could say that for any theory t to be true, all its sentences α must be true, and what it means for any α to be true is that a, where a is a sentence in the metalanguage we call normal language. But this would mean that a and α are strictly translations of one another in two different languages. If a theory is going to be explanitory of phenomena, then sentences like “light of such and such wavelength is predominantly reflected from the apple’s surface while other visible wavelengths are predominantly absorbed” have to have more content than “the apple is green”. If they mean the same thing, as sentences in Tarski’s definition of truth must, then theories can’t do any explaining.
So how else can we argue for Egan’s law?
You seem to be confusing your observation that a stick was bent with an actual stick bending.
The difference being that the mere observation of a stick that is bent does not have (in the case of it being in a glass of water) all of the other observational properties of a bent stick.
If, when you put a stick in water, it had all the other observational properties of a bent stick (example: you put your hand in the water and feel the bend in the stick) then you would conclude that "water bends sticks" and this would add up to normality.
But that's not what happens, so you conclude that the stick didn't actually bend. But you don't just throw away your observation of "I saw the stick bend" either. Instead, you use another theory that can explain the visual appearance of a bent stick without the stick needing to actually bend.
The fact that you observed X is not overturned by a theory that says you couldn't have. Instead, the observation overturns the theory.
As to external world skepticism, etc. Egan's law does not, strictly speaking, falsify them. But it renders them improbable. External world skepticism does not predict a blue sky as well as physics does. It doesn't make the statement that the sky will be blue. Physical realism combined with out knowledge of physics does make this statement. This makes physical realism more probable than external world skepticism. If it did not seem that, in principle, experiments regarding reality were able to explain it than we wouldn't use experiments and probably would be required to believe something like external world skepticism.
Incidentally, physics DOES deny, in some senses, that "the sky is blue," without denying that it appears blue. Blueness, as it turns out, is not a primary property (and it is only by not looking at history that we don't realize that this is a revolutionary discovery) the sky doesn't have "blueness" inside of it. Nevertheless, optics can tell us why the sky appears blue, without some blueness being inherent in the sky.
I may be confusing them, but it was my intention to draw out a distinction between 'appearance' sentences and 'fact stating' sentences, so as to show that 'normality' couldn't include any of the latter. That's the whole substance of my argument against Egan's law.
This depends on how you read Egan's law: as a heuristic or (as I put it in my original post), an a priori necessa... (read more)