It's a juicy prospect for a fast-developing industry: billions in federal grants for experimentation on human embryos.

Experienced grant writers must be revving up their search engines by now, since state grants for such research are already becoming available in states like Connecticut and Illinois and, of course, California, that bellwether of the surreal American future.

This session, Congress got behind this Next Big Thing, voting to expand embryonic stem cell research. But for the moment this rush to experiment on human embryos has been thwarted by a presidential veto, which the House failed to override.

But only for the moment. This is but a pause in the march of scientism, not a stop. After all, it's just one more slight little ethical boundary to be crossed on man's march toward physical and mental perfection, aka The Abolition of Man. That was the title of C. S. Lewis' percipient essay on the subject more than half a century ago.

Didn't this pro-life president himself authorize research on stem cell lines derived from already destroyed embryos? The moral of that story: One step down this slope quickly leads to another.

And yet George W. Bush balked at taking this latest one: "I felt like crossing this line would be a mistake, and once crossed we would find it almost impossible to turn back."

But wouldn't most of these discarded embryos be destroyed anyway? That's the standard argument offered in favor of embryonic research, and it opens up enough ethical questions to fill a talmudic treatise.

Yet all the rationalizations can't quite disguise the line that is being crossed here - for this time the embryos would be destroyed with the encouragement, indeed the monetary incentive, of the American taxpayer. That is, We the People. The ethical responsibility would be ours - not that of a fertility clinic and its clients.

The next ethical ridge to be crossed would then loom ahead: If it's permissible to experiment on embryos destined to be destroyed, why not on terminally ill patients, or prisoners on Death Row, or, well, the list would surely grow.

The case for embryonic experimentation isn't dubious just ethically but scientifically. To quote Robert P. George, a law professor at Princeton who served on the President's Council on Bioethics:

"Researchers know that stem cells derived from blastocyst-stage embryos are currently of no therapeutic value and may never actually be used in the treatment of diseases. . . . In fact, there is not a single embryonic stem cell therapy even in clinical trials. (By contrast, adult and umbilical cord stem cells are already being used in the treatment of 65 diseases.) All informed commentators know that embryonic stem cells cannot be used in therapies because of their tendency to generate dangerous tumors."

All of which leads Professor George to suspect that the clamor for embryonic stem cell research isn't really about using these early-stage blastocysts but exploiting more fully developed embryos, say those 16 to 18 weeks old, when the stem cells would be less likely to grow out of control.

Slate magazine's resident bioethicist, Will Saletan, outlined just such a program not long ago in his five-part series "The Organ Factory: The Case for Harvesting Older Human Embryos."

There's a short name for the kind of industry Mr. Saletan envisions: fetus-farming. Conclusion: Bioethics should never be confused with ethics.

The good news is that both houses of Congress also passed a bill - unanimously - that would outlaw the practice of growing embryos for scientific research. But how soon before that becomes the next taboo to be broken?

Embryonic research can also be challenged on economic grounds. Economists call it the problem of Opportunity Cost. That is, every dollar or million dollars invested in embryonic stem cell research cannot be invested in other forms of research. For example, research using stem cells derived from umbilical cord blood or the placenta. That kind of science offers considerable promise. And no ethical problems.

Yet the enthusiasts for embryonic stem cell research tend to oppose more federal support for research involving adult stem cells, and also funding for programs to develop stem cells without destroying human embryos in the process.

A bill embodying both aims was just defeated in the House - even as a majority of its members voted to support research using human embryos.

Embryonic research and embryonic research alone has become the cause du jour of the scientific and entertainment industry.

Given the choice between the ethically prudent course and going where no man has gone before, or dared to go, there is something in man that cannot resist the oldest temptation: Eat of this Tree of Knowledge and ye shall be as gods! No matter what false hopes may be raised, no matter what ethical boundaries crossed. Call it the Frankenstein Syndrome.