That such series exist is an empirical fact, which constitutes the verifiability of physics.
"Mysticism and Logic and Other Essays"
Bertrand Russell
I conclude, therefore, that no valid objection exists to the view which regards sense-data as part of the actual substance of the physical world, and that, on the other hand, this view is the only one which accounts for the empirical verifiability of physics.
"Mysticism and Logic and Other Essays"
Bertrand Russell
Now verifiability is by no means the same thing as truth; it is, in fact, something far more subjective and psychological.
"Our Knowledge of the External World as a Field for Scientific Method in Philosophy"
Bertrand Russell