Full Idea
In almost every act of our perceiving faculties, observation and inference are intimately blended. What we are said to observe is usually a compound result, of which one-tenth may be observation, and the remaining nine-tenths inference.
Gist of Idea
Most perception is one-tenth observation and nine-tenths inference
Source
John Stuart Mill (System of Logic [1843], 4.1.2), quoted by Peter Lipton - Inference to the Best Explanation (2nd) 11 'The scientific'
Book Reference
Lipton,Peter: 'Inference to the Best Explanation (2nd ed)' [Routledge 2004], p.204
A Reaction
We seem to think that his kind of observation is a great realisation of twentieth century thought, but thoughtful empiricists spotted it much earlier.