(LONG) "I Don't Know" as a Good Answer in Ethics

[The Grand Nudger]

To ensure charitability I will simply quote the definition offered by Shafer-Landau: "The view that moral features are natural (i.e. not supernatural) features, whose existence can be confirmed by means of the natural sciences."

Okay

So, happiness can be gauged by the instruments of science. A scientist can measure the levels of serotonin and dopamine present in the brain. These are indicators of happiness. Therefore, a hedonist (for example) has a scientific observable thing to measure with its moral meterstick. Since the hedonist is measuring a natural phenomenon, that refutes premise 2.

Okay.

The problem is here that science fails to supply value here. Can science even supply value? Science can only verify if happiness exists or not. Science cannot verify that happiness is good.

If happiness -is- what a hedonist is referring to when they use the term "value".....then science has indeed supplied and verified a demonstration of value.  Exclaiming that science cannot verify happiness is good is question begging regardless of whether or not the hedonist who makes such a claim is correct in doing so.  Not only this, by any competent use of the term and understanding of the proposition it both can, and has.  

Mind you, I don't agree with the hypothetical hedonist in this....simply pointing out that, as stated, this isn't a cogent objection.

(the open question argument as proposed by Moore, by the by, actually is an argument over semantics. Notably exposed as such by a moral naturalist not needing to object to this argument in the first place. Perhaps moral virtues are not directly reducible to natural properties in some general sense...it's certainly no moral naturalists view that every natural property is a moral property...but it is their view that all moral properties have natural properties, and that associated moral properties have common natural properties.)