Obama’s executive order reversed restrictions placed on the research by his predecessor, George W. Bush, which freed up laboratories to start working with the cells, which can give rise to any kind of cell in the body.

Cardinal Justin Rigali of Philadelphia, chairman of the U.S. Conference of Catholic Bishops, said “This action is morally wrong because it encourages the destruction of innocent human life, treating vulnerable human beings as mere products to be harvested.”

Now that Mr. Obama has lifted the restrictions, Catholic theologians have been debating how embryonic stem cell research can be made “less morally repugnant”, in the words of one theologian, Father Thomas J. Reese, senior fellow at the Woodstock Theological Center of Georgetown University, who then suggested several ways the Obama administration could find middle ground.

His suggestions included not creating embryos for the sole purpose of research but instead using only excess embryos produced at fertility clinics that are scheduled to be destroyed anyway. He also said researchers should show that the work they are doing can’t be done with non-embryonic stem cells, and that the research done using the embryonic stem cells should try advancing toward the goal of using only non-embryonic stem cells.