DM: How would you be aware of language itself, and thus of reason, without the senses? You wouldn't.
1.I regard reason as prior to language. Apart from reason, there would be no faculty for learning language in the first place.
2.You could learn language in the Matrix. You could learn to associate a word with a simulated object. So even if sensation were illusory, the illusion would be sufficient to learn how to manipulate linguistic tokens, just as a pilot can learn to maneuver a plane in a computer simulation.
3.Again, though, the actual question at issue is not whether the senses are reliable, but for what are they reliable?
I rely on the senses to tell me that a concrete object exists. But I don’t rely on the senses to tell me what, exactly, that object is really like, apart from the senses.
DM: Again, how would you know the concepts "grass" "blue" and "green" without sense experience?
SH: You’re confusing two different things. The relation between word and object is an arbitrary social convention.
I can learn what a word means if a word is generally associated with a particular sight or sound or scent or taste or texture.
But that issue is distinct from whether the word successfully picks out the insensible properties of the sensible object.
If the object is really red, but consistently appears to be blue, then I can learn the meaning of the words, as well as using the words to pick out the corresponding objects—without, however, assuming that the object is actually red rather than apparently red.
The primary qualities of the object may be quite different from the secondary qualities of the object, while the secondary qualities of the object may, in fact, be purely subjective (e.g. qualia).
But as long as there’s a regular correlation between the token and the object it betokens, you can learn what words mean and how to use them to navigate and manipulate your environment even if your precept is a dummy at several removes from what the object generating the stimulus is really like.
What we need is not an alethic relationship between A and B, but simply a regular correlation between A and B.
DM: What is the mind, or mental registration, without the senses? I'm not talking here about illusory sense experience, I'm talking about absolute skepticism towards your perceptions. If you had no sense input, let's imagine you were born in a sensory deprivation chamber, floating in some viscous liquid, and you had no input from the senses of any sort...
The point I'm making is that you trust your senses to develop your mental processes, like language, which reasoning is completely dependent upon. And all of the concepts you use in making propositions are pretty meaningless if your perception of those concepts is distorted.
1.You seem to be a radical empiricist, treating the human mind as a blank slate.
I don’t share your tabula rasa empiricism. I regard the senses as a source of knowledge, but not the only source of knowledge.
Unless, for example, the mind had an innate capacity to classify sensory input, it would never learn anything from raw sensory input. The mind must bring a set of general categories to bear in order to sort the concrete particulars.
Everything cannot be abstracted from the particular, for an empty mind merely receives and reproduces external impressions. It doesn’t interpret or rearrange the impressions according to a logical taxonomy.
2.And as I just explained, it would be possible to acquire true concepts and workable definitions even if we systematically misperceived our surroundings.
3.However, that doesn’t follow from my position. It goes back to the question of what the senses are for. Reliable for what?
I rely on my senses to tell what there is (with reference to concrete objects or effects), but not to tell me what these (concrete) objects are ultimately like.
So, according to my expectation, the senses do no misperceive or distort reality. It’s not the perception that’s mistaken, but a mistaken construal of what perception can yield.
DM: I agree that some of your responses are sufficient to my objection, but I don't see how you can get past trusting in your own perceptions, and applying a sort of double standard to scientific observation.
SH: I do trust my senses. But with a couple of qualifications:
1.My trust is indexed to my expectation. What are they for? What’s their purpose?
2.I also trust my senses because I believe that they were designed to perform a certain function.
If, however, I believed in naturalistic evolution, then that would induce in me a radically sceptical outlook on the reliability of the senses as well as the reliability of the mind.
3.You continue to miss the point that I am not applying a double standard to science.
To the contrary, in critiquing scientific realism I am applying a scientific standard to metascientific issues.
According to a scientific analysis of sensation, apparently colored objects are really colorless. Color (as well as other secondary qualities) is subjective, not objective.
So science is imputing the optical illusion to secondary qualities.
According to a scientific analysis of sensation, what we perceive is not the object as it is, but encoded information about the object. Electromagnetic encoding. Electrochemical encoding.
So science is responsible for setting a blackbox between the input and the output, plaintext and ciphertext.
DM: I haven't presented the brain in a vat as some primary argument, but as a reminder that if you doubt your perceptions, you start down a slippery slope towards such uber-skeptical positions.
Except that science is pushing you down the slippery slope.
At least, the way you define and delimit science.
DM: Such as doubting the reliability of perception?
SH: Regarding my distinction between rational and irrational doubt:
1.I have reason to believe that naive realism is false.
I can’t prove that. It could be that objects are really smaller at a distance, that oars really bend in water.
But it’s simpler to account for that sort of phenomenon as an observer-dependent optical illusion.
We could, of course, spend a lot of time on simplicity as a criterion, and the tradeoff between one type of simplicity and another, but since you’re not a naive realist yourself, I’m spared that Herculean effort.
2.But once we admit a gap between appearance and reality, it is very difficult to measure the gap.
How many layers intervene? Does the percept bear any direct or indirect resemblance to the sensible?
3.And, for reasons I’ve already given, this is more of a problem for you than it is for me.
The irony is that I’m both to the right and to the left of you and Babinski.
In some ways I’m far more sceptical than the two of you are, but—as a Christian—I also have a back-up system which you do not.
4.On the other hand, I don’t have reason to believe that I’m a captive of the Matrix or a brain-in-a-vat.
Also, these sceptical scenarios fudge in various ways. To propose them in the first places assumes a degree of detachment which the hypothetical denies.
5.It’s possible to dream up some indetectible illusion, viz. the Cartesian demon. Since the hypothetical is framed to be unfalsifiable, it succeeds at that hypothetical level.
But why believe the hypothetical in the first place? In the nature of the case, there can never be any evidence for such a proposition,since what renders it unfalsifiable is also what renders is unverifiable.
6.And even if I were inclined to take that hypothetical the least bit seriously, I also believe that certain theistic arguments undercut the Cartesian demon, viz. the moral argument, certain versions of the ontological argument, the principle of sufficient reason, a psychological version of the teleological argument, &c.
7. To doubt scientific realism due to Cartesian demons, or modern versions thereof (The Matrix, the brain-in-a-vat) would be a case of irrational doubt.
But there are many intellectually respectable reasons to doubt scientific realism or direct realism.
To take the example that you yourself cited by Exbrainer, even if there’s a workable correlation between my X-percept and the underlying Y-reality, the details of the X-percept do not carry over to the Y-reality—just as the details of the ATM keyboard bear no resemblance to the greenbacks.
Absence the transference of X-perceptual properties to Y-properties, scientific realism is up against a wall.
That follows from your own assumptions. And that’s a case of rational doubt.
8. It can also lead to global scepticism, although the Christian has a safety net which you do not.
9.Speaking of which—there are, in addition, many intellectual respectable reasons to believe in the existence of God as well as the inspiration of the Bible.
10.And revelation supplies an intersubjectival check on our subjective impressions.