There is a crucial difference between these two cases. All other integrations into a super-science, or sciences dealing with entities and properties apparently qualitatively distinct, was achieved by saying that really some of the entities and properties were not as they appeared to be; by making a distinction between the underlying (not immediately observable) entities and properties and the phenomenal properties to which they give rise. Thermodynamics was conceived with the laws of temperature exchange; and temperature was supposed to be a property inherent in an object. The felt hotness of a hot body is indeed qualitatively distinct from particle velocities and collisions. The reduction was achieved by distinguishing between the underlying cause of the hotness (the motion of the molecules) and the sensations which the motion of molecules cause in observers. The former falls naturally within the scope of statistical mechanic—for molecules are particles’ the entities and properties are not of distinct kinds. But this reduction has been achieved at the price of separating off the phenomenal from its causes, and only explaining the latter. All reduction from one science to another dealing with apparently very disparate properties has been achieved by this device of denying that the apparent properties (i. e. the ‘secondary qualities” of colour, heat, sound, taste, etc.) with which one science dealt belonged to the physical world at all. It siphoned them off to the world of the mental. But then, but when you come to face the problem of the sensations themselves, you cannot do this. If you are to explain the sensations themselves, you cannot distinguish between them and their underlying causes and only explain the latter. In fact the enormous success of science in producing an integrated physico-chemistry has been achieved at the expense of separating off from the physical world colours, smells, and tastes, and regarding them as purely private sensory phenomena. The very success of science in achieving its vast integrations in physics and chemistry is the very thing which has made apparently impossible any final success in integrating the world of the mind with the world of physics.
C. S. Lewis on the Dangers of Extrapolating from Past Scientific Success
This is in response to a Secular Outpost post by Keith Parsons.
I am afraid you don't have Lewis right here at all. In fact, when you read him, and when I read him, it is as if we are reading the same words, but getting an entirely different message. Now I could be being exasperatingly generous, or maybe you aren't giving him a fair shake, but somehow we just aren't seeing the same things. Lewis isn't romanticizing dryads, etc. What he is doing is pointing out the problems with taking successful scientific developments and extrapolating from those to other areas of discourse where treating something else in the same way as science treated another area results in bad conclusions.
In the case of psychology, I take it that since you and I are close to the same age, you remember what psychology departments were like in the early 1970s. They were filled with people, following B. F. Skinner, who thought to really treat human beings in a scientific manner we had to stop talking about consciousness. It's the extrapolation from previous successes in science, the idea that we can look at the trajectory of science and make confident predictions about how science is going to have to treat certain types of subject matter, that we get into trouble.
Now the reason this is not an attack on science is because this history of science should really teach us that we can't plot the course of future scientific success. Science progresses sometimes by coming up with successful reductions, and sometimes progresses by recognizing that reductionism isn't going to work. Cognitive science, while not going anti-naturalistic, has come to reject the idea that consciousness has to be denied (although it is still very much a scientific mystery). The behaviorist hegemony which seemed to pervasive in psychology in my undergraduate days (the entire ASU philosophy department was one huge rat lab) is now considered a Dark Age.
This passage, from the Abolition of Man, helps to see that Lewis is complaining about extrapolations from science, not about science itself.
From this point of view the conquest of Nature appears in a new light. We reduce things to mere Nature in order that we may `conquer' them. We are always conquering Nature, because `Nature' is the name for what we have, to some extent, conquered. The price of conquest is to treat a thing as mere Nature. Every conquest over Nature increases her domain. The stars do not become Nature till we can weigh and measure them: the soul does not become Nature till we can psychoanalyse her. The wresting of powers from Nature is also the surrendering of things to Nature. As long as this process stops short of the final stage we may well hold that the gain outweighs the loss. But as soon as we take the final step of reducing our own species to the level of mere Nature, the whole process is stultified, for this time the being who stood to gain and the being who has been sacrificed are one and the same. This is one of the many instances where to carry a principle to what seems its logical conclusion produces absurdity. It is like the famous Irishman who found that a certain kind of stove reduced his fuel bill by half and thence concluded that two stoves of the same kind would enable him to warm his house with no fuel at all. It is the magician's bargain: give up our soul, get power in return. But once our souls, that is, ourselves, have been given up, the power thus conferred will not belong to us. We shall in fact be the slaves and puppets of that to which we have given our souls. It is in Man's power to treat himself as a mere `natural object' and his own judgements of value as raw material for scientific manipulation to alter at will. The objection to his doing so does not lie in the fact that this point of view (like one's first day in a dissecting room) is painful and shocking till we grow used to it. The pain and the shock are at most a warning and a symptom. The real objection is that if man chooses to treat himself as raw material, raw material he will be: not raw material to be manipulated, as he fondly imagined, by himself, but by mere appetite, that is, mere Nature, in the person of his de-humanized Conditioners.
I originally brought this up in connection with a passage from Richard Swinburne about how some of these past scientific successes were achieved.
It was Lewis who said, "It is the glory of science to progress." But progress may not go in the same direction as past progress.