The social and political climate surrounding human embryonic stem cell (hESC) research is constantly changing, as is the science, with new developments occurring at a regular pace. Rapid changes can exacerbate fears, and fears often contribute to sweeping pronouncements and prohibitions that may not, ultimately, withstand rational scrutiny. This collection of essays represent one of the most philosophically engaged and biologically informed discussions of the central ethical issues raised by stem cell research to date.

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• Do blastocysts have moral status?
  
• Do stem cells themselves have a special status?
  
• Can "surplus" embryos respectfully be used for research?
  
• Should human-animal chimeras be created?
  
• Should women be paid for their eggs?
  
• What is the best mechanism for dealing with deep disagreements in a democratic society?

The carefully constructed arguments that seek to answer these questions should contribute to and encourage more rigorous public debate about the ethics of stem cell research.