Lord Caitanya’s philosophy — that is the greatest contribution to the world — that these living entities who are hankering after happiness by different process. By material process, by philosophical process, by mental concoction or mental process they are trying, and Lord Krsna also said — they are trying — but that happiness is available when your senses or consciousness are pure.

From Srila Prabhupada’s lecture, March 5, 1969, Hawaii (the day after
Gaura-Purnima)