Source identified1
“The strongest man in the world is he who stands most alone.”
Dr. Stockmann turns social isolation into a claim about independence of conviction: within the play’s conflict, standing without majority approval becomes evidence of his determination to continue rather than a neutral rule that solitude always makes a person stronger.
Source note: An Enemy of the People, Act V, final exchange; R. Farquharson Sharp translation represented by Project Gutenberg #2446. Dr. Thomas Stockmann says the line to his family after deciding to remain in town, so the dramatic speaker and contentious political context are essential to the quotation.