... Quinn misunderstands their position.

... Hume's distinction between matters of fact and relations of ideas prevents the difficulty Quinn imagines.

... Quinn's imaginary scenario does not resemble anything we would recognize as a desire and does hence not constitute a counterexample.

... Quinn's objection was already conclusively refuted by Hume in his Treatise.

... Quinn's own conception cannot work because reason must be "the slave of the passions."