# 2013-05-08 - Closer To Truth - Can Science Provide Ultimate Answers [YouTube](https://www.youtube.com/watch?v=j65pZMkQv48) Duration: 00:07:18 ## Transcript ### Robert Lawrence Kuhn 00:00:00 - 00:00:16 David, you are a great espouser of the power of good explanations, the scientific method to make progress. Indeed, you're an optimist very strongly in this regard. Let me turn it around. What are the limits of science? ### David Deutsch 00:00:16 - 00:01:11 One of the most important limits of science is that it isn't philosophy. Science only deals with the physical world and to discover regularities in the physical world and also means of controlling the physical world. So that's one limitation and what we call scientism is the purported application of science to problems that are really philosophical. Such as the question of whether animals really feel pain or not. We can tell whether animals' nerves are excited and whether their brains react to that, but whether an animal feels pain in the sense that humans do or merely reacts in the sense that a robot does. That is ultimately a matter of philosophy because it's only philosophy that can determine the criterion for science to use when trying to distinguish between those cases. ### Robert Lawrence Kuhn 00:01:11 - 00:01:13 Okay, that makes sense. ### David Deutsch 00:01:13 - 00:01:19 So that's a limit of science. Trying to reach into philosophy is scientism. ### Robert Lawrence Kuhn 00:01:19 - 00:01:50 Now the history of the progress of science has been one of expanding its boundaries. So we can't say for sure even today where those boundaries are because as far as we know it has been constantly expanding and some would say that ultimately it can expand not necessarily to answer every possible question of existence, but to answer every question that can be answered and then there would be no room for philosophy or theology or whatever else. ### David Deutsch 00:01:50 - 00:02:17 We can't predict the future growth of knowledge. That by the way is another limitation of science, but I think it's much more likely that the thing that is omnipotent, the thing that can reach to everywhere and solve every problem is not science narrowly conceived, but reason. The quest for good explanations reaches far beyond science into all these philosophical areas. ### Robert Lawrence Kuhn 00:02:17 - 00:02:22 So you differentiate good explanation from science. It's not a one-to-one relationship. ### David Deutsch 00:02:22 - 00:02:29 No, science is a special case of good explanations. It's good explanations applied to questions about the physical world. ### Robert Lawrence Kuhn 00:02:29 - 00:02:34 Some would say that the only kinds of good explanations are scientific ones. ### David Deutsch 00:02:34 - 00:02:43 Yes, well I would say to those people that that theory is not part of science and therefore it rules itself out. ### Robert Lawrence Kuhn 00:02:43 - 00:03:14 Okay, now if we look at the concept of explanation there are philosophers of science who are empiricists in which they say that the claim that anything is really real is impossible and extends beyond the human capacity. We can say there are regularities, there are observations, the observations always occur, all the things that you can literally predict, but to go that step to say it's an explanation is a step too far. ### David Deutsch 00:03:15 - 00:04:46 Yes, by the way this trope of saying that science can only deal with predictions but not with understanding what reality is like is usually part of a piece of bad philosophy that's trying to rule out a piece of real science, as happens in quantum theory when people try to say that parallel universes aren't real because we can't directly see them, we can only see their results. But the thing is it doesn't work as a foundation for science, that theory. Consider for example the theory that dinosaurs existed. Now nobody will ever see a dinosaur as the creationists never tire of pointing out, nobody has ever seen one or will ever see one, at least not the ones that we claim existed in the past. All we see are fossils. So this empiricism would say science can't make any claim about dinosaurs, it can only make a claim about fossils. This fossil will be found in a stratum with this fossil but in a different stratum from this other fossil. Now this drains science of its entire purpose which is to understand reality. Nobody would be interested in fossils if they were just patterns in stones, there are plenty of other patterns in stones and some of them are more interesting than the fossils and certainly easier to come by. ### Robert Lawrence Kuhn 00:04:46 - 00:05:09 Well, the empiricists would say I am protecting science, I am protecting it from doing things that are irrational. Maybe those bones will be taken as an example and bad theories made of those and so I'm going to keep science very constrained on the track of truth and not let it bloat beyond ### David Deutsch 00:05:10 - 00:06:42 This is why we have a criterion for what is or isn't scientific, namely testability. So the scope of science keeps growing as we find ways of making testable theories about things where previously we couldn't. A prime example is cosmology, which if you look in an old dictionary you will see cosmology listed as a branch of philosophy, but if you look in a modern dictionary it's listed as a branch of physics. That's an example of the totalitarian character of physics that intends to envelop everything else. At any one moment we can tell exactly where the limit of science is using the criterion of testability, testable theories. We have testable theories of dinosaurs so it's legitimate to talk about dinosaurs as they were hundreds of millions of years ago as well as they are now in the form of fossils. The criterion of good explanation, that an explanation should be hard to vary, implies that criterion for good science but it also tells us what is good philosophy and that is vital. In the case of empiricism it tells us that that is bad philosophy because you could rule out anything that was real by that criterion. In fact the sense impressions that seemed like a good basis for science at the time when empiricism was invented a few hundred years ago turn out to be highly complex things which are not observed. ### Robert Lawrence Kuhn 00:06:42 - 00:06:44 So it's self-defeating. ### David Deutsch 00:06:44 - 00:06:45 Self-defeating, yes. ### Robert Lawrence Kuhn 00:06:45 - 00:06:57 So as you look at the flow of science from the past and into the future would you say that ultimately there are limitations but we can't know where they are today? ### David Deutsch 00:06:57 - 00:07:17 That's exactly right. Science has limitations, reason however does not and there will be ultimate limits of science beyond which progress will only ever be made with philosophy broadly speaking. We don't know what those are, they are almost certainly beyond the current limits of science.