positron, the positive particle regarded as the polar opposite of the
negative electron, he remarks: 'A positron is a hole from which an
electron has been removed; it is a bung-hole which would be evened up
with its surroundings if an electron were inserted. ... You will see
that the physicist allows himself even greater liberty than the
sculptor. The sculptor removes material to obtain the form he desires.
The physicist goes further and adds material if necessary - an
operation which he describes as removing negative material. He fills up
a bung-hole, saying he is removing a positron.' Eddington thus shows to
what paradoxical ideas the scientist is driven, when with his
accustomed forms of thought he ventures into regions where the
conditions necessary for such forms no longer exist; and he concludes
his remarks with the following caution: 'Once again I would remind you
that objective truth is not the point at issue.'

By this reminder Eddington shows how far science has reconciled itself
to the philosophic scepticism at which man's thinking had arrived in
the days of Hume. In so far as the above remark was intended to be a
consolation for the bewildered student, it is poor comfort in the light
of the actions which science has let loose with the help of those
unknown entities. For it is just this resignation of human thought
which renders it unable to cope with the flood of phenomena springing
from the sub-material realm of nature, and has allowed scientific
research to outrun scientific understanding.

1 E. du Bois-Raymond: Investigations into Animal Electricity (1884).
Galvani published his discovery when the French Revolution had reached
its zenith and Napoleon was climbing to power.

2 The above account follows A. J. von Oettingen's edition of Galvani's