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Great thoughts reduced to practice become great acts.
— William Hazlitt ‧ Table Talk: Essays On Men And Manners (1821-1822)

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The saying connects a thought with the act that puts it into practice. Greatness moves from the idea into the deed through that change. Its emphasis is on carrying thinking into action, presenting practical effort as the way an imagined possibility becomes something accomplished.
Context reviewed