Fight, fight, fight. This is a relationship marked by sharp edges. Both signs like to lead, direct and have the last word. A positive result of these two meeting is on the other hand that their considerable differences normally creates mutual respect. But beyond respect, what might there be? Aries is idealistic and romantic, Capricorn cynical and realistic. Capricorn is steady, serious, cool and detached, Aries impatient, fiery, playful and childish. They do indeed share a somewhat simplified conception of the world: in the aries case as divided into what I want and not want, what is good and bad - and in Capricorn into the useful and pointless, straight or crooked, reliable or dismissable. And because of this they communicate well.
But good as it is, communication and respect aren't enough. It just too much of Capricorn playing the part of father/mother figure with the child that is Aries. Professionally this could certainly be productive and a perfect balance of initiative and organisation, but it just doesn't seem quite natural enough emotionally and romantically. The spontaneous and easygoing flow of feeling is blocked, also when that great Capricornian sense of dry humour and self-distance comes sneaking. They think differently, direct their energy differently, and they just cannot, cannot stand, none of them, to ever give up stubbornly thinking that they're right.