Possibly. In order for a patent claim to be valid under Title 35 of the United States Code, it has to meet five fundamental requirements:
1. patentable subject matter - a stapler or a method for purifying silicon would generally be patentable; a variation on existentialism or a new religious belief system would not be.
2. originality - it can't have been invented by someone else; if you "discovered" an invention by overhearing a discussion about it in a restaurant, you can't race to the patent office and try to get a patent on it before its inventor gets around to filing.
3. novelty - it must be a new idea, not one already in use or one that has already been written about.
4. utility - a "useful" invention is one "which may be applied to a beneficial use in society, in contradistinction to an invention injurious to the morals, health, or good order of society, or frivolous and insignificant" (Justice Story [383 U.S. 519, 533])
5. non-obviousness - the patent must describe something that would not be obvious to someone reasonably well-trained in the field.