This will hardly be the first time that two TED speakers have verbally jousted oon the TED stage. Here, sets of TED speakers who have disagreed — either in an official debate or in separate talks — to give you a taste of what to expect at TED2013, where the TED Blog will be reporting live every second.

Paul Zak vs. Molly Crockett: Is oxytocin the moral molecule?

In these two talks given a year apart, neuroscience experts Paul Zak and Molly Crockett disagree on what we can say about oxytocin.

Paul Zak: Trust, morality -- and oxytocin?Paul Zak: Trust, morality — and oxytocin? Morality is a distinctively human trait and it might be because of the hormone oxytocin. In this talk from TEDGlobal 2011, neuroeconomist Paul shares his 10-year search for what he calls “the moral molecule” and reveals his studies on how oxytocin boosts trustworthiness, empathy and even the desire to give money to charity.

Molly Crockett: Beware neuro-bunkMolly Crockett: Beware neuro-bunk Neuroscientist Molly Crockett wants everyone to spot “neuro-fiction” — claims that overshoot our current understanding of the brain. Crockett evokes Zak’s work with oxytocin. According to Crockett, studies on oxytocin “are scientifically valid and they have been replicated, but they’re not the full story.” She explains, “Other studies have shown that boosting oxytocin increases envy, it increases gloating. Oxytocin can bias people to favor their own group.”

Peter Diamandis vs. Paul Gilding: What will the future look like?

Because these two speakers expressed such different views at TED2012, TED Curator Chris Anderson invited the pair onstage for a formal debate.

Rick Warren vs. Dan Dennett: Do our lives have purpose?

Dan Dennett couldn’t help but respond directly to Rick Warren at TED2006, after hearing his talk.

Rick Warren: A life of purpose Rick Warren: A life of purpose At TED2006, pastor Rick Warren said, “I believe spiritual emptiness is a universal disease.” He explained his belief in God, and how he thinks each one of us is here for a specific purpose that matters, and describes his crisis of purpose in the wake of releasing a best-selling book.

Dan Dennett: Responding to Pastor Rick Warren Dan Dennett: Responding to Pastor Rick Warren Speaking at the same conference, philosopher Dan Dennett suggests that religions are natural phenomenon, evolving over time to survive. Dennett says that life — both ours and that of animals — has been designed by evolution, and lacks an individual purpose.

Stewart Brand vs. Mark Z. Jacobson: Nuclear energy?

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Before you watch this debate from TED2010, try this experiment: Ask yourself, who do you agree with now? Watch the debate. And then — ask yourself again.

Note: This post was originally published on August 6, 2012, and was updated with a new introduction and set of examples on Feb. 13, 2013.