Never enough?

I referenced Bill McKibben's Enough: Staying Human in an Engineered Age yesterday, in connection with Alexander's & Radiance's engaging dialogue about the moral standing of sentient AIs. I agree: if machines someday learn to feel as well as compute, humans (or post-humans) will be morally obliged to acknowledge their claim to moral recognition and respect.

But I also agree with the tenor of Betsy's question: should we want to create sentient, sophisticated synthetic life? Must we? Is it "inevitable" that we'll try, or can we still have a significant conversation about whether to apply the brakes?

Not sure I agree with McKibben, but I think we owe  it to ourselves to think about what he says:

Faced with a challenge larger than any we've ever faced — the possibility that 
technology may replace humanity — we need to rally our innate ability to say no. 
We will be sorely tempted to engineer our kids, but it's a temptation that we need 
to resist as individuals, and to help each other resist as a society...

Once we start down the path of turning ourselves into machines, of writing ineradicable programs for our proteins, there will be no way, and no reason, to turn back. We'll do what our programming indicates, never knowing how much choice we really have...