Kirsten Walsh writes…
In an earlier post I demonstrated that, in his early optical papers, Newton is working with a clear distinction between theory and hypothesis. Newton takes a strong anti-hypothetical stance, giving theories higher epistemic status than hypotheses. Newton’s corpuscular hypothesis appears to challenge his commitment to this anti-hypothetical position. Today I will discuss a second challenge to this anti-hypotheticalism: Newton’s use of queries.
Newton’s queries have often been interpreted as hypotheses-in-disguise. But in his early optical papers, Newton’s queries are not hypotheses. In fact, he is building on the method of queries prescribed by Francis Bacon, for whom assembling queries is a specific step in the acquisition and development of natural philosophical knowledge.
To begin, what is Newton’s method of queries? In a letter to Oldenburg, Newton explains that
- “the proper Method for inquiring after the properties of things is to deduce them from Experiments.”
Having obtained a theory in this way, one should proceed as follows: (1) specify queries that suggest experiments that will test the theory; and (2) carry out those experiments.
He then lists eight queries relating to his theory of light and colours, e.g.:
- “4. Whether the colour of any sort of rays apart may be changed by refraction?
“5. Whether colours by coalescing do really change one another to produce a new colour, or produce it by mixing onely?”
He ends the letter, saying:
- “To determin by experiments these & such like Queries which involve the propounded Theory seemes the most proper & direct way to a conclusion. And therefore I could wish all objections were suspended, taken from Hypotheses or any other Heads than these two; Of showing the insufficiency of experiments to determin these Queries or prove any other parts of my Theory, by assigning the flaws & defects in my Conclusions drawn from them; Or of producing other Experiments which directly contradict me, if any such may seem to occur. For if the Experiments, which I urge be defective it cannot be difficult to show the defects, but if valid, then by proving the Theory they must render all other Objections invalid.”
While Newton’s method of queries is experimental, it does not appear to be strictly Baconian. For the Baconian-experimental philosopher, queries serve “to provoke and stimulate further inquiry”. Thus, for the Baconian-experimental philosopher, queries are part of the process of discovery. However, for Newton, queries serve to test the theory and to answer criticisms. Thus, they are part of the process of justification.
Newton uses queries to identify points of difference between his theory and its opponents. For example, in a letter to Hooke he writes:
- “I shall now in the last place proceed to abstract the difficulties involved in Mr Hooks discourse, & without having regard to any Hypothesis consider them in general termes. And they may be reduced to these three Queries.  Whether the unequal refractions made without respect to any inequality of incidence, be caused by the different refrangibility of several rays, or by the splitting breaking or dissipating the same ray into diverging parts;  Whether there be more then two sorts of colours; &  whether whitenesse be a mixture of all colours.”
And in a letter to Huygens, Newton says:
- “Meane time since M. Hu[y]gens seems to allow that white is a composition of two colours at least if not of more; give me leave to rejoyn these Quæres.
“1. Whether the whiteness of the suns light be compounded of the like colours?
“2. Whether the colours that emerg by refracting that light be those component colours separated by the different refrangibility of the rays in which they inhere?”
In both cases, Newton is using queries to steer the debate towards claims that can be tested and resolved by experiment. On both occasions, Newton devotes a considerable amount of space to discussing the experiments that might determine these queries.
These early queries are not hypotheses. Rather, they are empirical questions that may be resolved by experiment. This is not merely a matter of semantics. In the same letter to Hooke, Newton demonstrates this by distinguishing between philosophical queries and hypothetical queries. A philosophical query is one that can be determined by experiment, a hypothetical query cannot. Newton argues that philosophical queries are the only acceptable queries. He equates hypothetical queries with begging the question.
In his later work, Newton’s queries become increasingly speculative, suggesting that they function as de facto hypotheses. Does Newton ultimately reject his early ‘method of queries’?
Next Monday we’ll have a guest post from Greg Dawes on Galileo and the Experimental Philosophy.