The trouble with this understanding is that it is often too ambitious. In chemistry, for
example, it was only in the twentieth century that such explanations began to be possible,
because it was only then that chemical interactions began to be explained in terms of the
properties of fundamental particles such as electrons. For such particles, it is arguable that
we can give explanations in terms of real essences, because we can claim that all there is to
being (for example) an electron, is having its properties of mass, charge, and spin.
However, this does not mean that chemistry did not provide any scientific explanations
prior to the twentieth century. The notion of scientific explanation thus needs to be
expanded beyond the original Aristotelian conception, to include explanations of the kind
sought by the founders of the Royal Society. (The approach needed for this expansion was
already present in the medieval notion of ‘saving the appearances’, but this notion tended
to be put forward as an alternative to the Aristotelian approach to science, rather than as an
addition to it.) In Aristotelian terms, this kind of explanation will involve identifying things
of a certain kind, and establishing experimentally that things of this kind behave in
characteristic ways, but not trying to account for this behaviour in terms of the real essence
of those things.
A simple example would be identifying samples of gold with a spectrometer, and
determining that they are insoluble in nitric acid, but soluble in aqua regia (a mixture of
nitric and hydrochloric acid). However, contrary to Locke’s claim, admitting scientific
explanations of this type need not be accompanied by rejecting any scientific role for real
essences. Instead, it gives them a further role; we can explain the truth of generalisations
like these ones about the solubility of gold by saying that they result from the underlying
real essence of gold, and we can pursue an understanding of this real essence by attempting
to determine how it can explain such generalisations. This in fact is exactly what scientists
do; they look for an underlying structure that confers upon gold both its power to affect
spectroscopes in certain ways, and its capacities to dissolve or resists dissolution in various
substances. So the real implication of the Royal Society’s approach to scientific explanation
is that the notion of such explanation should be broadened, instead of altered to
eliminate real essences. This broadening will still leave real essences playing a fundamental
role, since they will be the ultimate goal and ending point of scientific explanation.