There is no arena in which vanity displays itself under such a variety of forms as in conversation.

[Il n’est point d’arène où la vanité se montre sous des formes plus variées que dans la conversation.]

Germaine de Staël (1766-1817) Swiss-French writer, woman of letters, critic, salonist [Anne Louise Germaine de Staël-Holstein, Madame de Staël, Madame Necker]

Germany [L’Allemagne], Part 1, ch. 11 “Of the Spirit of Conversation” (1813)
    (Source)

(Source (French)).

Sometimes misattributed to Marguerite Gardiner (Lady Blessington), due to this quote (there attributed to de Stael) being included in the Preface to R. R. Madden, The Literary Life and Correspondence of the Countess of Blessington, Vol. 1 (1855).