Massimo Pigliucci has a rather damning review of The Moral Landscape here. Peter Beattie responds with defence of Harris over here at Butterflies and Wheels. In each case, there is already a pretty good thread in response.
Just some quick observations - with more to come tomorrow.
I have some quibbles of my own about the Pigliucci review. The para about how creepy it would be if the state had effective lie detectors and started to use them on us routinely gets some sympathy from me, but it seems out of place. I'm not sure what it contributes at that point in the review, and the review would have been fine without it. Also, I do get sick of the use of this word "scientism" to beat Harris with. In the end, the problems with The Moral Landscape aren't so much about thinking that all problems can be solved by science. Even if Harris may sometimes seems to think that, the real problems are elsewhere. In fact, the endnote in which Harris says that he is not distinguishing sharply between the sciences and other empirically-based areas of study, such as history, seem fair enough to me.
However, I do agree with Pigliucci that Harris has conspicuously failed to derive "ought" from "is" in the way that he sometimes seems to think he can do.
Recall that there really are various ways to derive "ought" validly from "is". The much criticised David Hume was well aware of the most important of these. For example, you can derive an "ought" conclusion from an "is" premise if you also use an "ought" premise. The problem relates to deriving "oughts" without using any "oughts" in your premises. Thus, Hume would have had no problem with an argument such as:
P1. If the sky is white then we ought to slay the purple frog.
P2. The sky is white.
C. We ought to slay the purple frog.
That's perfectly valid reasoning, though the premises are, I take it, not true. P2. might be, I suppose, but P1. sounds implausible.
More importantly, Hume was well aware that you can derive an "ought" of practical rationality if you include premises that relate to someone's goals, values, desires, or something of the kind. Thus, I consider the following to be valid:
P1. Amara's goal is to turn the sky green.
P2. If Amara slays the purple frog, the sky will turn green.
C. (Other things being equal) Amara ought to slay the purple frog.
P1. Bertie desires Amara's love.
P2. Bertie will obtain Amara's love if he gives Amara some chocolate.
C. (Other things being equal) Bertie ought to give Amara some chocolate.
P1. Bertie places a value on obtaining chocolate.
P2. Bertie can obtain chocolate by looking in the cupboard.
C. (Other things being equal) Bertie ought to look in the cupboard.
There are also some logical tricks that I mentioned in an earlier post.
P1. Bertie is amorous.
P2. Bertie is not amorous.
C. Bertie ought to slay the purple frog.
Notoriously, you can derive any proposition validly from contradictory premises. Getting from "is" to "ought" this way isn't a very useful trick, however, since it depends on logically impossible (because internally contradictory) situations obtaining.
P1. Everything Amara says is true.
P2. Amara says, "Bertie ought to slay the purple frog."
P3. Bertie ought to slay the purple frog.
I suppose this might be useful in practice if we actually knew that Amara is always right, but there's still something fishy (if not amphibian) about it. It gives us a method of knowing that some "ought" claims are true. But the conditions in the premises are not what make it true that Bertie ought to slay the purple frog. What might make it true is that slaying the purple frog will achieve some goal of Bertie's, such as causing rain to fall from the white sky. There's also the small issue that we at least had to mention an "ought" claim in our premises, which seems like cheating.
For various reasons, these sorts of arguments do not get us from "is" to "ought" in ways that would amount to solutions of the "is/ought" problem. That's mainly because the problem is how to get from "is" to "ought" in a way that does not presuppose any "oughts" in the premises and does not depend on such things as people's actual values, goals, desiderative sets, affective attitudes, and so on. Also, in this area of philosophy we really want to know what set of "is"-type facts can actually make it true that we ought to do certain things. It's not enough that we can be confident of someone's advice - that's not what we were asking about.
Since Harris presupposes that we ought to maximise the well-being of conscious creatures, he has, indeed, conspicuously failed to get from "is" to "ought" in the way that philosophers mean. He is using an "ought" as a premise. Even if he is right that we ought to maximise the well-being of conscious creatures, he has not provided a solution to the "is/ought" problem. That's pretty fundamental.
This doesn't make the book worthless. It merely doesn't do one of the things that it seemingly claims to do. All of which is unsurprising. At this point in history, we've reached a situation where a claim to have solved the "is/ought" problem should be looked at with much the same scepticism as a claim to have invented a perpetual motion machine. Or a claim to have produced a logically compelling ontological argument for the existence of God. If someone claims to have done any of these things, it's just as well that there are people around to check it out. But you can be pretty sure in advance that the person cannot produce what is advertised.