Full Idea
We know things through demonstration, by which I mean a scientific deduction, and by 'scientific' I mean a deduction by possessing which we understand something.
Gist of Idea
We can know by demonstration, which is a scientific deduction leading to understanding
Source
Aristotle (Posterior Analytics [c.327 BCE], 71b17)
Book Reference
Aristotle: 'Posterior Analytics (2nd ed)', ed/tr. Barnes,Jonathan [OUP 1993], p.2
A Reaction
This is a distinctively Aristotelian account of what science aims at, and which seems to have dropped out of modern accounts of science, which are still under the influence of logical positivism. Time to revive it.