Field* claimed that given that there are two incompatible senses of the term ‘mass’ used in textbooks on the special theory of relativity and there is no way available to decide which of the two incompatible senses that Newton would have used, the term ‘mass’ must be indeterminate as to its reference. Field briefly considers the possibility that Newton’s term ‘mass’ did have a determinate sense, but that we simply do not know which sense that is, but he finds this possibility to be implausible. In the vein of verificationism, if there is to be a difference in meaning then there must be some way to tell the difference. Yet, how is the question of Newton’s sense of the term ‘mass’ any different to the question of what he ate for breakfast on his sixteenth birthday? There is nothing implausible about being unable to find any evidence one way or the other to decide what he had for breakfast that day, and yet this lack of any evidence to decide between theories about what he might have had for breakfast that day does not lead us to conclude that his meal was indeterminate: neither kippers nor not-kippers. Why should it be any different for the concept expressed by Newton with his use of the term ‘mass’? It might be countered that we could know what Newton had for breakfast given some counterfactual circumstance X. Yet, what principled basis is there for determining the counterfactuals that are reasonable to decide whether or not something is verifiable in principle? Had it been the case that we were present at the meal, we could verify a theory as to what he had for breakfast. Well, had we taught Newton special relativity he would have told us which meaning of ‘mass’ he had referred to with his preceding use of the term ‘mass’. Why should one counterfactual be granted any more plausibility than the other?
*Field, H., ‘Theory Change and the Indeterminacy of Reference’ (1973) Vol. 70 No 14 Journal of Philosophy pp. 462-81 at p. 473
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