Consider this dialog:

Student: "Wise master, what ought I do?"

Wise master: "You ought to help the poor by giving 50% of your income to efficient charity and supporting the European-style welfare state."

Student: "Alright."

*student runs off and gives 50% of his or her income to efficient charity and supports the European-style welfare state

This dialog rings true as a fact about ought statements - once we become convinced of them, they do and should constrain our behavior.

But my dialogs and your dialogs contradict each other! Because if "ought" determines our behavior, and we can define what "ought" means, then we can define proper behavior into existence - a construction as absurd as Descartes defining God into existence or Plato defining man as both a hairless featherless biped and a mortal.

We must give up one, and I say give up yours. "ought" is one of those words that we are not free to define - it has a single meaning. Look to its consequences, not its causes.