I passionately believe that’s it’s not just what you say that counts, it’s also how you say it - that the success of your argument critically depends on your manner of presenting it.

De Botton is stressing that persuasion is never purely a matter of logical content: tone, timing, tact, and rhetorical form shape whether an audience can hear an idea at all. The quote aligns with his broader project of making philosophy practical—showing how emotional intelligence and social psychology condition “rational” debate. A sound argument can fail if delivered with contempt, aggression, or pedantry, because listeners experience the manner as a threat or humiliation and become defensive. Conversely, clarity, humility, and generosity can give difficult truths a chance to land. The line is a reminder that communication is ethical as well as intellectual: how we speak reveals our respect for others and can determine whether truth becomes shared understanding.