One cool judgement is worth a dozen hasty councils. The thing to do is to supply light and not heat.

Wilson contrasts calm, disciplined judgment with impulsive group deliberation. “Cool judgement” suggests reasoned appraisal—facts weighed, passions checked—while “hasty councils” evokes committees or advisers rushing to decide under pressure. The second sentence sharpens the ethical ideal for public leadership: to “supply light” is to clarify issues, educate opinion, and guide action through understanding; to “supply…heat” is to inflame feeling, partisan anger, or panic. Read as a maxim of statesmanship, the line argues that the best political counsel is illumination rather than agitation, and that durable decisions come from temperate reasoning rather than excited debate.