Ghosts, Catholics, and Protestants
I tried to explain how the fact that the events of Hamlet are initiated by a ghost would have looked to Shakespeare’s audience.
Protestants would have been inclined to believe that the ghost was the devil. The various suicides and murders would have represented damned souls. Catholics, by contrast, would have been more willing to believe that the ghost could have been the soul of Hamlet’s father.
The play itself, it seems to me, does not obviously settle the question of what, exactly the ghost was.
I asked you to read Hobbes for two reasons. First, his materialist psychological theory is quite different from those on offer from Augustine and Descartes. He also has a challenge for Descartes’s dream argument that’s worth thinking about, particularly if you’re writing a paper on that question (see ch. 2, par. 9).
The other reason for reading Hobbes was to get a flavor of how the anti-Catholic case was made. Chapters 45 and 47 are devoted to trying to show that the Bible does not say anything incompatible with Hobbes’s materialism (it’s an uphill battle, as Jon and Rebecca noted).
That raises a question: why is there a long tradition of thinking otherwise? Hobbes’s answer was that the offensive ideas entered into the Christian tradition from Greek philosophy. Think of the Platonists who convinced Augustine that there is such a thing as immaterial substance: that’s the sort of thing that he has in mind. These doctrines were sustained by those who benefit from having people believe in them: the leaders of the church.
Incidentally, while Hobbes’s attacks are explicitly directed at the Catholic church, the last paragraph in ch. 47 (and some other things he wrote) suggests that they were veiled ways of attacking some of the Protestant churches, such as the Scottish Presbyterian church, that sought political influence.
Sources
If you’re curious about this sort of thing, I highly recommend the third chapter of John Dover Wilson, What Happens in Hamlet.
Chapter 19 of Keith Thomas’s Religion and the Decline of Magic is also relevant.