Just as thermometers are a tool that measures temperature as relative degrees,
Amusing -- those are a direct quantification of temperature. Degrees Celsius for example goes to degrees Kelvin rather well. They use arbitrarily fixed points above zero K -- but the IQ scale does not do this.
Now, of course, IQ is not g. And we have no means of quantifying g.
I think maybe you are under the misapprehension that by "intellectual capacity" I was saying "intelligence". If I had meant "intelligence" I would have said "intelligence".
Recently I stumbled upon Richard Carrier's essay "Are We Doomed" (June 5, 2009), when asked to comment about the Singularity, said the following:
What do you think?