   Many non-intentional relations hold of concrete particulars in space and time. If and when they do, their relata cannot fail to exist. If Cleopatra kisses Caesar, then both Cleopatra and Caesar must exist. Not so with intentional relations. If Cleopatra loves Caesar, then presumably there is some concrete particular in space and time whom Cleopatra loves. But one may also love Anna Karenina (not a concrete particular in space and time, but a fictitious character). Similarly, the relata of the admiration relation (another intentional relation) are not limited to concrete particulars in space and time. One may admire not only Albert Einstein but also Sherlock Holmes (a fictitious character). As the following passage from the Appendix to the 1911 edition of his 1874 book testifies, this asymmetry between non-intentional and intentional relations puzzled Brentano: