Seneca, Moral Epistle 59.1-2
“I got a lot of pleasure from your letter–permit me to use words commonly, without insisting on their Stoic meaning. We believe that pleasure is a vice. It may very well be. Still, we have the habit of using that term for characterizing a joyous feeling in the mind. I know that if we measure words by our dictionary that pleasure is a matter of bad repute and joy is available only to the wise.
Joy is the elation of a mind that relies in its own goodness and truth. Still, when we use it casually, we say we get great joy from a friend’s consulate, or their marriage, or the birth of their child. These things are not really joyous as much as the seeds of future sadness. Nope. Real joy is made to never stop, to never be turned into its opposite.”
Magnam ex epistula tua percepi voluptatem; permitte enim mihi uti verbis publicis nec illa ad significationem Stoicam revoca. Vitium esse voluptatem credimus. Sit sane; ponere tamen illam solemus ad demonstrandam animi hilarem adfectionem. Scio, inquam, et voluptatem, si ad nostrum album verba derigimus, rem infamem esse et gaudium nisi sapienti non contingere. Est enim animi elatio suis bonis verisque fidentis. Vulgo tamen sic loquimur, ut dicamus magnum gaudium nos ex illius consulatu aut nuptiis aut ex partu uxoris percepisse, quae adeo non sunt gaudia, ut saepe initia futurae tristitiae sint. Gaudio autem iunctum est non desinere nec in contrarium verti.