(For other posts in this series, see here.)

Reader Jeff asked three good questions about some of the issues I discussed in my series on the logic of science that I would like to address here. What follows are his questions and my responses.

“First, in Part II you discuss the concepts of Know-How and Know-Why. I am curious as to what extent these concepts might be applied to understanding the differences between the Hard Sciences (Physics, Chemistry, &c.) and the Soft Sciences (Psychology, Sociology, &c.) Are what we call Soft Sciences sciences at all?”

Science has considerable prestige as providing reliable knowledge and as a result many fields of study aspire to that label. But the issue of what distinguishes science from non-science is as yet unresolved. The know-how/know why distinction of Aristotle ceased to be considered viable as a means of distinguishing science from non-science when Newton came along. His laws of motion and gravity were spectacularly successful in explaining the motion of objects, especially the solar system. He thus provided the ‘know-why’ that had been previously missing from the purely empirical field of astronomy, lifting it into the realm of science.

But Newton’s laws had serious know-why deficiencies of their own because they had no explanation for why distant inanimate objects exerted forces on each other. Up until then, forces were believed to be exerted by contact, and the introduction of mysterious forces that acted at a distance was somewhat of an embarrassment. But the immense achievement of unifying our understanding of celestial and terrestrial motion led many to deem that what Newton had done to be unquestionably science, despite its lack of know-why for its major elements. Know-why ceased to be a requirement for science. This development was in some sense inevitable because we now realize that every theory is based on some other theory and that at some point we just have to say ‘and that’s just the way it seems to be’, without being able to elucidate any further.

The search for better ways to distinguish science from non-science went on. To be able to definitely say whether something belongs in some category or not (whether it be science or anything else) requires one to specify both necessary and sufficient conditions for belonging in that category. We can specify some necessary conditions for science. It needs, for example, to be empirical, predictive, and materialistic, and Thomas Kuhn added the condition that it also work within a paradigm. But suitable sufficient conditions are much harder to come by.

If a theory fails to meet the necessary conditions threshold, it means that it is definitely not science, which is why so-called ‘intelligent design theory’ has been deemed to be not science. But meeting the necessary threshold only allows us to conclude that the theory could be science, not that it definitely is.

This inability to say definitely that something is a science has not proven to be a problem for those areas (the so-called ‘hard sciences’ such as almost all areas of physics, chemistry, and biology) that are, by broad consensus, unambiguously considered to be science, because nobody except philosophers of science cares whether they meet any criteria or not. But it has proven problematic for the soft sciences, where there is no such unanimity. The scientific status of some areas of physics (such as string theory) has also been challenged on the grounds that it has as yet not generated any predictions that can be tested empirically.

“Second, in Part VII you use the electron as an example of a universal claim that can never be proven because we can never test each and every electron in the universe. I wondered if it would be possible to make the claim that any particle that does not have the mass and charge of an electron is not an electron in the same way that we can state that any atom the does not have solely a single proton is not Hydrogen?”

You can define away the immediate problem by saying that the electron is a particle having a set number of properties. But this simply defers the problem. It does not let us off the hook because we cannot say (for example) that every hydrogen atom has one of these particles because we cannot test each and every atom to see if that is true. We simply have to make the universal claim that it does, and that cannot be proven either.

“Third, in Part X you write “that however much data may support a theory, we are not in a position to unequivocally state that we have proven the theory to be true.” Where does this leave Laws such as the laws of gravity and thermodynamics? Do we no longer speak of Laws as such?”

The terms ‘law’ and ‘theory’ do not have any ranking order epistemologically in that there is no sense in which a law is truer than a theory. For example, Newton’s laws of motion are known to have limited validity and not be true when it comes to the very small or the very fast, while Einstein’s theories of special and general relativity are believed to have no violations.

What gets called a ‘law’ and what gets called a ‘theory’ differ in what they imply, though accidents of historical naming can also play a role. A law tends to be an empirical universal generalization of observed relationships between measurable quantities. So the law of conservation of energy says that if we were to measure the sum of all the energy components of a closed system at one time, that total will remain the same if we measure all the components at another time. Newton’s laws of motion give us the relationships between forces and mass and acceleration. Boyle’s law gives us the relationship between the pressure and volume of a gas. These are all empirical generalizations and none of them try to explain why these relationships hold true.

A theory, on the other hand, consists of a more complicated explanatory structure that specifies the elements of the system that it deals with, as well as how those elements behave and the relationships among them. A theory might be able to explain what undergirds a law, though it rarely proves it because of the many extra assumptions that are needed. So, for example, the kinetic theory of gases tells us what elements comprise an ideal gas and how they interact with each other and their container. Using that theory, we can understand where Boyle’s law comes from. Similarly, quantum theory tells us that the conservation of energy is connected to the invariance of laws under time translations, i.e., that the laws of science do not change with time.