Deducing Moral Judgements

"You cannot deduce a moral judgement from facts about the natural world," says Peter Singer in agreement to the is/ought problem.

"In every system of morality, which I have hitherto met with, I have always remarked, that the author proceeds for some time in the ordinary way of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when of a sudden I am surprised to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is, however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, it's necessary that it should be observed and explained; and at the same time that a reason should be given, for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it. But as authors do not commonly use this precaution, I shall presume to recommend it to the readers; and am persuaded, that this small attention would subvert all the vulgar systems of morality, and let us see, that the distinction of vice and virtue is not founded merely on the relations of objects, nor is perceived by reason." David Hume A Treatise of Human Nature (1739)

So how is one to decide a moral judgement?

According to philosophers, like David Hume or Peter Singer, one needs to use more formal logic to deduce a conclusion. One can use facts. One can make arguments. But one shouldn't suggest, as Hume might state, that because x is, or is not, that y ought, or ought not, be done. 

I'm not sure anyone who deduces moral judgements will accept this, but if you're open to the idea, leave a comment and I can say more.