The quote from P.G. Wodehouse's "Mostly Sally" reflects the idea that marrying the right partner requires a shared intellect and compatibility. The phrase suggests that a woman who takes on the challenge of being with the speaker would need to possess an extra measure of intelligence, potentially implying that the speaker himself may not always be the most competent or sensible partner.
Wodehouse's humorous tone highlights the complexities of relationships, particularly in the context of marriage. The emphasis on having "brains enough for two" underscores the importance of mutual understanding and partnership, hinting that a successful marriage may rely as much on wisdom and insights as on love and affection.