What, in your view, were the significant factors which brought about conflict in Northern Ireland?

There seems to be a common feeling among the political and opinion leaders: the sense that some conflicts have last forever and will, somehow, always remain. This goes along with the assertion that some people can't come over their ancient hatreds or differences: Israeli and Palestinians, Russians and Chechens, Irish and British. Not only is this untrue, but it moreover conveys the idea that the northern-Irish conflict is based on ethnic criteria, on an ontological opposition between the protestant Anglo-Normans and the catholic Celts.
To me, the roots of the conflict have to be sought for in a political explanation that gathers three factors: property, power and perception.