Emerson isn't simply saying that thinkers should also be practical—he's claiming that intellectual power without the stamina to *endure* is mere parlor philosophy. The phrase "strong to live" suggests something fiercer than competence; it means the courage to withstand disappointment, solitude, and the gap between vision and reality. A teacher might spend years developing brilliant pedagogical theories, but without the grit to weather resistant administrators, burned-out colleagues, and slow progress, those ideas remain locked in notebooks. The great soul, as Emerson sees it, must have the constitution of both the scholar and the pioneer.