Full Idea
Logic and observation alone do not force a scientist to reject a scientific claim if experimental observations so not turn out as expected. The scientist must reject something of the initial set of claims, but that is a matter of choice.
Gist of Idea
Observation can force rejection of some part of the initial set of claims
Source
report of Pierre Duhem (The Aim and Structure of Physical Theory [1906]) by Stephen Boulter - Why Medieval Philosophy Matters 2
Book Reference
Boulter,Stephen: 'Why Medieval Philosophy Matters' [Bloomsbury 2019], p.53
A Reaction
This is a key point against any simplified Popperian notion of falsification. Tiny observations can't kill huge well supported theories.