Suppose John loves Mary "for being a baroness" (and for what follows from being a baroness), but does not love him for any other reason. But in fact, unbeknownst to both of them (errors in the geneology, say)[note 1] On the other hand, if Mary is a commoner, then in typical cases, we would say that John, who loves her for being a baroness, doesn't actually love her. Instead, he loves a Baroness Mary who does not exist.
But, pace Kierkegaard, it seems that sometimes loving y for P does entail loving y. This will be true at least in the case where y has P and P is a lovable quality of y. Granted, such a love is presumably a conditional one, and hence inferior to the love that Kierkegaard rightly values, but it is still a love. Moreover, the example of Duchess Mary thought to be a baroness shows that sometimes x loves y for P and y lacks P, but nonetheless x has a love for y there. This will be so for instance when y lacks P, but has a property that, in x's structure of beliefs, is more more lovable.
It could be said that if this is how things are, I've misdescribed John's love. He doesn't love Mary for being a baroness, but for being at least a baroness. Maybe--but the way I put it seems more natural. What makes her be at least a baroness is her being a baron, and it is for this that Mary loves him.
Hence, from "x loves y for having property P" it does not follow that x loves y. This gives a precise meaning to Kierkegaard's statement that to add reasons to love is to subtract from the love. In fact, it might be the case that that x loves y entails that x loves y for various properties, but that x loves y for some property only entails that x loves y in some cases, such as cases of y's essential properties like being a creature of God.
A different example of Kierkegaard's statement might be cases where x loves y for having P, and y has P, but we would hesitate to say that x loves y. This will be cases where the property P is not one that makes for the interpersonal love that is typically meant when we say x loves y. For instance, this will be true when the cannibal loves y for y's taste, and y in fact is tasty to the cannibal. Sure, we could say that the cannibal loves y, but she is loving y not in the way one loves a person, but in the way one loves a cake. But maybe these kinds of cases are just like the cases of a mistake about properties. For maybe the cannibal loves y not just for y's taste, but for y's being tasty and y's being food. But y, in fact, is not food (at least not in the normative sense).
Why do I care? For several reasons. First, I am interested in the phenomena of distorted love. Second, I am interested theologically in the ways one might misconceive of God and Christ and still count as believing.