Arguments in moral philosophy are rarely conclusive, partly because we each have mutually inconsistent intuitions.
So you can see in that passage Hobbes takes himself to be a moralist writing within the great tradition of moral philosophy.
The context of this was that Hume was applying for a chair in moral philosophy at Adumbral and the clergy at Adumbral was very much against him.
Ghosts, mediums, and miraculous cures by the intercession of saints play no role in his argument, which draws instead on quantum mechanics, neuroscience, and moral philosophy.
