In terms of movies, horror is the most philosophically rich of the various genres, generally giving a more truthful commentary on us humans than any of its generic brethren (science fiction is equally compelling as a literary genre, but it just hasn't lived up to its potential in film -- cf. Tarkovsky's religious mockery of one the great atheistic novels, Solaris, to catch my drift). Since my only costume for Halloween is a wet blanket, why not offer a series of double-feature suggestions as a way of getting into the spirit? I'm going to stay away from the ones everyone should've already seen (yes, Kubrick's The Shining is the greatest horror film ever made, end of discussion) and none by directors with the initials D.L. I plan on doing one a day, ending either with Halloween, or until I run out of categories, or I just get plumb sick of doing this. First up, the fear of the irrational, or, more appropriately, the fear of losing one's grasp on reality.
A common refrain in horror film criticism since the 70s has been that the genre makes us confront the faults in the architecture of reason. This critique usually goes by the name of postmodernism and its big bugaboo by the name of the Cartesianism. René Descartes had some difficulty reconciling how all the immaterial, mental stuff was able to effect changes in all the meaty stuff we call physical, creating the primary Cartesian dichotomy called mind-body dualism. No one's figured a way out of that mess yet, but who cares since we're talking about horror movies. The important point is that Descartes tended to privilege reason over all that biological machinery, so he gets the blame for all the scientistic / instrumentalist / phallocentric / logocentric / patriarchal domination that has supposedly developed since the 17th Century. (I remain skeptical of this demonization of the Rationalists for the simple reason that I'd prefer to live after the Enlightenment than before it.)