Well... you are certain that consciousness exists because you experience it: that is measuring.
As for explaining it, I guess it's more of a definitional problem than a physical one. I'm still confident that one day we'll be able to look at something and approximate how conscious it is.
Free will, on the other hand, requires supernatural phenomenons coming from outside the material world (dualism) to explain how we, humans, can make decisions free of any (or some) of the influences of the physical world. I don't buy it, and I believe the burden of proof falls on the ones who do.
As for explaining it, I guess it's more of a definitional problem than a physical one. I'm still confident that one day we'll be able to look at something and approximate how conscious it is.
Free will, on the other hand, requires supernatural phenomenons coming from outside the material world (dualism) to explain how we, humans, can make decisions free of any (or some) of the influences of the physical world. I don't buy it, and I believe the burden of proof falls on the ones who do.