Answer:
He means that truth alone triumphs over all, no matter how deserted h may be. he is strong for he stands for what is true, unlike the other town people easily influenced by public opinion.
Step-by-step explanation:
In Henrik Ibsen's play "An Enemy of the People", Dr, Stockmann had found out that the water in the bathing complex of the town had been contaminated. He accused the authorities of not taking any action to clean it, nor do they want to. The mayor of the town, who happens to be his brother, also doesn't think it is necessary to be checked.
When Dr. Stockmann discovered the contamination, he had given out a statement to warn others of the town. But he was instead asked to retract his statements, for it will only ruin the reputation of the town. Refusing to budge under pressure, he and his family ended up alone, being kicked out of their home, getting 'fired' from their jobs, and even asked to leave the town all due to "public pressure". But, at the end of the play, we find Dr. Stockmann declaring that "the strongest man is one who stands alone", implying that even if he is left alone, he will not comply to the pressure of the majority. He became the fear of the whole town, people and media agencies coming to him for help in keeping their businesses alive. He is strong, stronger than the others for he stands for the truth and truth always prevail in the end. There can never be any harm in standing up for what is true.