Why would you want to debate with an atheist? What would you gain? Nobody ever convinced anyone of the existence of G‑d through debate.

The atheist believes that the universe is cold and indifferent. The believer believes the universe is warm and caring. Show this person caring and warmth and perhaps then he will come to believe. And if not, you still made the universe a more caring and G‑dly place.

Rabbi Tzvi Freeman for Chabad.org