If we can invent pills that will make us happier, smarter or more productive, is that a good thing? Or does being human necessarily include some difficulties, some tragedies?

Is joy a right? Or is pain our natural bane? It is a quandary that strikes at the very core of our existence and one so new that a word -- neuroethics -- had to be coined to describe it.

Like many newly sprouted scientific words, neuroethics has old roots. Neuro comes from the Greek word neuron, which means sinew or cord. Ethics is also from a Greek word, ethika, which derives from ethos, meaning character, nature or disposition. The word ethos itself derives from an even older Indo-European word for "self."

While the word may be fresh out of the box, neuroethical dilemmas already are all around us. Consider the "glass half full" sort of guy who is not clinically depressed but finds he feels better if he takes Prozac. Or the college student who finds she is more focused when taking Ritalin, even though she doesn't have attention deficit disorder. Or the law partner who learns that she can sleep only a few hours per night and still feel alert by taking a legal, non-addicting drug with no side effects.

These people are all taking medications that act on the brain, on the way they think and feel. If who we are, our sense of self, is defined by the workings of the brain, then how much can or should we be fooling with that? Put another way, is it a good idea to use meds that can change our moods on demand, like an emotional Botox?

Two and a half years ago, UCSF professor emeritus Zach Hall chaired a neuroethics conference co-hosted by UCSF and Stanford University. UCSF's Hall, Bernard Lo and Howard Fields were joined by ethicists, neuroscientists and journalists from all over the country to explore precisely these sorts of questions. Since then, many other voices have joined in the debate, including author Francis Fukuyama, who argues in his book Our Post-Human Future that biotechnology should be regulated before we lose the biological anchor that provides social and political stability. Others worry that we might all end up like the characters in the Philip K. Dick story who wake up every morning and use a machine to imprint themselves with whatever emotion they want to feel for the day. If they don't feel like using the machine, there is even a setting they can choose that will make them feel like using it.

But is all the existential hand-wringing justified? As some neuroethicists are quick to remind us, humans have always modified the way they think: Think alcohol. Or caffeine. Or nicotine, kava, or other substances. Why is it so terrible, they ask, for people to feel better, smarter, and more successful, especially without the negative side effects of drugs like alcohol or nicotine?

The ultimate neuroethics debates will occur in the coming years as we begin to understand even more about how the brain works. Already, the drug modafinil provides an energy boost without the side effects of amphetamines or even caffeine. Future drugs, some now in the testing stages, boost memory and learning. MRI scanners can increasingly profile our state of mind and some day may be able to reveal what we are thinking.

It looks like there is a big future for this brave new word.