Ideas won't keep; something must be done about them.

Whitehead’s aphorism stresses that ideas are perishable unless translated into action. An insight, plan, or theory does not “keep” the way a stored object does: it fades from memory, loses urgency, or becomes obsolete as circumstances change. The line also implies an ethical and practical imperative—thinking is incomplete without implementation, testing, or embodiment in institutions, habits, experiments, or works. In a broader Whiteheadian spirit, it aligns with a process-oriented view of reality: value lies in becoming and doing, not in static possession. The quote is often used to encourage follow-through, innovation, and the conversion of abstract ideals into concrete practice.