I am firm. You are obstinate. He is a pig-headed fool.

Bertrand Russell
Bertrand Russell (1872-1970) English mathematician and philosopher
Comment, The Brains Trust, BBC Radio (1948-04-26)
    (Source)

Offered as a game, "Conjugations" (today referred to by linguists as "Russell Conjugations" or "Emotive Conjugations"). The publication The New Statesman and Nation subsequently ran a competition for similar "irregular verbs," which were later printed (1948-05-15), along with the quote from Russell.

Sometimes misattributed to British journalist Katharine Whitehorn.