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Does Newton feign an hypothesis?

Kirsten Walsh writes…

Newton’s famous pronouncement, Hypotheses non fingo, first appeared in 1713, but Newton’s anti-hypothetical stance is present as early as 1672, in his first papers on optics.  In his first publication, he introduces his notion of certainty, and insists that his doctine of colours is a theory; not an hypothesis:

    For what I shall tell concerning [colours] is not an Hypothesis but most rigid consequence… evinced by ye mediation of experiments concluding directly & without any suspicion of doubt.

Despite these clear anti-hypothetical themes, a corpuscular hypothesis lies beneath Newton’s theory of light and colours.  What are we to make of this?  Is Newton guilty of feigning an hypothesis? Is Wolff correct when he says that Newton “indulges in hypotheses in those very areas in which they think he abstained from employing them“?

To begin, what does Newton mean by Hypotheses non fingo?  ‘Fingo’ has been variously translated as ‘frame’, ‘make’, ‘imagine’ and ‘devise’. Experts argue that ‘feign’ is the most appropriate translation.  While it has a variety of meanings, such as to form, to invent, to forge, or to suppose erroneously, the word ‘feign’ also carries the nuance of pretence, counterfeit, or sham.  Thus, they argue that while Newton indeed conceived or framed hypotheses, he did not attach any special epistemic status to them.  He maintained a clear demarcation between theories that were supported by experimental results and hypotheses that were merely unsupported speculations.

Now let’s take a closer look at Newton’s early optical papers.  Newton claims that his doctrine of colours is a theory, not an hypothesis, for three reasons:

  1. It is certainly true, because it is supported by (or deduced from) experiment;
  2. It concerns the physical properties of light, rather than the nature of light; and
  3. It has testable consequences.

These are the three key aspects of Newton’s early methodology.  He refers to them again and again throughout the debate that followed the publication of his first optical paper.

Newton explicates his corpuscularian view in his first optical paper and describes light rays as substantial bodies.  But when his opponents accuse him of hypothesising, Newton argues that he is not guilty.  Firstly he argues that this hypothesis is not necessary for his explanation of colours.  Secondly he argues that he attaches no special epistemic merit to his hypothesis because:

  1. It is not supported by experiment;
  2. It concerns the nature of light; and
  3. It has no testable consequences.

While Newton never gives up his corpuscularian view, he attempts to explicate and promote his theory without referring to it.  He argues that he doesn’t need to provide any hypothesis on the nature of light – his theory on the properties of light is sufficient on its own.

I claim that Newton isn’t guilty of violating his anti-hypothetical stance.  He demonstrates that he can distinguish between theory and hypothesis, giving the former higher epistemic status than the latter.  He does not pretend to have empirical support for his corpuscular hypothesis, nor does he try to ‘prop it up’ on other grounds.  Perhaps he regrets having ever opened the proverbial can of worms, for the next time he explicates his theory of light and colours, he does so without any reference to the corpuscular hypothesis or the nature of light.

That Newton can tell the difference between good scientific explanations and speculations is further supported by his use of queries in these early optical papers, but more on this next time.  To conclude,  I think Newton is not guilty of feigning an hypothesis.  What do you think?

2 thoughts on “Does Newton feign an hypothesis?

  1. I would probably not worry too much about the proper translation of ‘fingo’. What I find much more interesting is his use of ‘hypotheses’. After all he uses the word in a very unusual way, so that he is required to provide a definition immediately afterwards. The OED only lists one usage in this way before Newton, Nathanael Carpenter in 1635, compared to many other uses of the word current at the time. At least in one passage of the Opticks (p. 242 in the 1718 edition), hypothesis seems even to have even employed in the more common way by Newton . Given that the word ‘speculatio’ was already partially associated with the modern slant, why is he opting for hypothesis?
    An hypothesis on his stance however: Wouldn’t it be possible to understands his position in the General Scholium of the Principia more as one on method than on methodology (or in modern terms a position on discovery and not on justification)? The way he puts it there is not that he has a problem with a hypothesis of gravitation because it is not testable, but that it would not have been originally deduced from phenomena and then generalised by induction according to his regula philosophandi. It’s thus not about support by experiment or testability, but about the very way any causal explanation of gravitation could be found.

  2. Hi Gerhard,

    Thank you for your comments.

    You say that Newton “uses the word [‘hypothesis’] in a very unusual way”. I don’t think his usage is so very unusual. In early modern natural philosophy, the word ‘hypothesis’ could be used in a number of different ways. For example, it referred to generalisations, metaphysical principles, or even explanatory systems. From the 1660s, as the distinction between experimental philosophy and speculative philosophy developed, ‘hypothesis’ also began to be used as a synonym for speculation. The degree to which early modern experimental philosophers were anti-hypotheses varied. Some experimental philosophers sought to find a legitimate role for hypotheses within the experimental method, others made use of hypothetical explanations in a self-conscious or apologetic fashion, others sought to prevent all discussion of hypotheses, regarding (hypothesis-free) experimental philosophy as the only legitimate way forward in natural philosophy. While not all early modern experimental philosophers agreed with Newton’s brand of extreme anti-hypotheticalism, they would certainly have recognised and understood this position. That Newton introduces certainty as a condition of calling something a ‘theory’ is more unusual – most experimental philosophers were probabilists or inductivists.

    I like your point about the discovery versus justification of Newton’s explanation of gravitation. I need to give this some more thought, but in his early optical papers, Newton sometimes seems to talk about discovery (e.g. when he talks about deducing theories from the phenomena) and sometimes justification (e.g. his method of queries).