In a debate called ‘Scientists vs Philosophers’ (on YouTube), the host opens up with this question:
“Why is it that so many physicists are bashing philosophers nowadays?”
Take Stephen Hawking.
As many people (especially philosophers!) know, Stephen Hawking (1942–2018) wasn’t very keen on philosophy and made that clear a couple of times in his later life.
The following is what Hawking himself said on the subject of philosophy:
“Traditionally these are questions for philosophy, but philosophy is dead. Philosophy has not kept up with modern developments in science, particularly physics. Scientists have become the bearers of the torch of discovery in our quest for knowledge.”
What’s more, Hawking made the following incredible claim about his own (philosophical!) position:
“Model-dependent realism short-circuits all this argument and discussion between the realist and anti-realist schools of thought.”
So perhaps it wasn’t philosophy simpliciter that Hawking was against; but only philosophy “which has not kept up with modern developments in science”. (Many philosophers themselves have said the same about their fellow philosophers.) As it is, I don’t believe that Hawking was actually being selective about philosophy; though it’s worth raising that possibility.
It’s strange, then, that in his book The Grand Design (cowritten by Leonard Mlodinow) Hawking himself indulges in a fair bit of philosophy.
So here’s a taster of Hawking’s philosophy:
“There is no picture- or theory-independent concept of reality. Instead we will adopt a view that we will call model-dependent realism: the idea that a physical theory or world picture is a model (generally of a mathematical nature) and a set of rules that connect the elements of the model to observations. This provides a framework with which to interpret modern science.”
Sure, it might have been the case that Stephen Hawking didn’t see his own model-dependent realism as a philosophical position. He might have seen it as a simple description of the methodologies and facts of physics. Yet that too would have been both a philosophical position and also very naïve.
In addition, it’s also worth noting here that Hawking classed himself as “a positivist”. This is what he wrote in his book The Universe in a Nutshell:
“Any sound scientific theory [] should in my opinion be based on the most workable philosophy of science: the positivist approach put forward by Karl Popper and others… If one takes the positivist position, as I do, one cannot say what time actually is. All one can do is describe what has been found to be a very good mathematical model for time and say what predictions it makes.”
The words above make Hawking’s rejection of philosophy even stranger.
As it is, this essay is going to concentrate on Hawking’s philosophical words on on the realism-vs.-anti-realism debate — as it specifically relates to the uncertainty principle.
Firstly, a few words on realism in science.
Realism vs. Anti-Realism
In the following Stephen Hawking mentions “realism”. He wrote:
“Though realism may be a tempting viewpoint, as we’ll see later, what we know about modern physics makes it difficult one to defend.”
Obviously it’s the case that realism is most certainly a philosophical — i.e., not a scientific — term.
On the surface at least, Hawking seems to be taking some kind of anti-realist position. This, by definition, must be as philosophical a position as realism. Yet the fact is that (as it were) practising scientists — and perhaps even theoretical physics — needn’t take any position on the realism-anti-realism debate. They could simply “shut up and calculate”. In addition, most physicists probably never even think about this issue at all. Indeed other physicists would argue that taking a realist or anti-realist position wouldn’t — and doesn’t — make the slightest bit of difference to what they do.
I said earlier that Hawking adopted some kind of anti-realist position. More accurately, however, he adopted what he called “model-dependent realism” (as discussed in the introduction).
So not only did Hawking indulge in philosophy: he even went so far as to concoct his own philosophical theory! (Of course model-dependent realism isn’t entirely Hawking’s work.)
Now for the uncertainty principle.
Hawking on the Uncertainty Principle
Stephen Hawking dug himself even deeper into his own philosophical hole when he discussed the uncertainty principle. He wrote:
“For example, according to the principles of quantum physics, which is an accurate description of nature, a particle has neither a definite position not a definite velocity unless and until those quantities are measured by an observer.”
Some physicists may argue that there’s not much — or even any — philosophy in the words above. Yet that simply isn’t the case.
Firstly, stating that
“a particle has neither a definite position not a definite velocity unless and until those quantities are measured by an observer”
is an explicitly philosophical position. Indeed Hawking didn’t even say that
we cannot know if a particle has a definite position/velocity before measurement.
He stated that
a particle has neither a definite position nor a definite velocity unless we measure such a thing.
That is Hawking’s statement about the ontological situation of x before measurement. In addition, Hawking was saying something about x.
Again, many physicists have argued that (other) physicists needn’t say anything about whether a particle has a “definite position” or a “definite velocity” before being “measured”. Raising that very question (or subject) is itself philosophical. Instead, all scientists really need is the mathematical formalism (including the wave function), the predictions, the experiment itself, the observations, etc.
After all, from a purely scientific point of view, if a scientist can’t know whether the particle has a definition position, etc. before the measurement or experiment, then what scientific purpose does a postulation of “its” previous status actually serve? (This is a point that Werner Heisenberg, Wolfgang Pauli, etc. made in the 1920s and 1930s.)
All this means that when Hawking was being philosophical when he so much as raised these issues. Indeed he offered his own philosophical position on them!
Hawking continued:
“It is therefor not correct to say that a measurement gives a certain result because the quantity being measured had that value at the time of the measurement.”
In the words above, Hawking became even more philosophical. That is, qua scientist, he didn’t need to say anything about what status the “quantity” had before measurement. But he did. Hawking took an explicitly philosophical position on this. That is, he said — or implied — that it is (philosophically) wrong to believe that
“a measurement gives a certain result because the quantity being measured had that value at the time of the measurement”.
On the other hand, Hawking believed that it is (philosophically) right to believe that
“in some cases individual objects don’t even have an independent existence” [i.e., before measurement].
But how could Hawking have known that?
In addition, he would have needed to defend his position philosophically — and many philosophers and indeed physicists have done so.
So the philosophical position may be one (or both) of the following:
(1) We can simply never know what state a particle (or “quantity”) had before measurement.
Alternatively:
(2) It makes no sense at all to believe x had a particular state before measurement.
Hawking seems to have opted for that latter philosophical interpretation when he said that these “individual objects [] exist only as part of an ensemble of many”. This is an indirect reference to the wave function. That is, there is an ensemble of individual objects until there’s an observation — and then we (as it were) bring about a single definite object. (Put differently: until the wave function is collapsed, we have an ensemble of individual objects.)
But note that not only was Hawking doing philosophy, a (quasi?)realist position is also hidden in his words. That is, Hawking did say something about the world (or individual objects) before any measurement. In detail, he wrote:
“In fact, in some cases individual objects don’t even have an independent existence but rather exist only as part of an ensemble of many.”
Thus Hawking believed that there was an “ensemble of many” individual objects (or quantities) before any measurement.
So isn’t the belief that there is an ensemble of many individual objects before measurement just as realist a position as the belief that there’s a definite object in a definite state before measurement?
In addition, isn’t it the case that in order to be consistent, Hawking should have said nothing about this previous state. He should have only talked about (in whichever order) the wave function (or the mathematical formalism) for the experiment, the experiment itself, the predictions, the observations and so on.
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