At school we learned opposite forces attract and like forces repel. The nucleus of most atoms contain several positively-charged protons clustered together, creating enormous forces of repulsion. The force that holds the nucleus together is strong, but in high energy states it is occasionally overcome, creating nuclear reactions.

Religions and political parties are like this. Broad churches of similar opinion can break apart when they are subject to heated issues. January saw the Anglican Church's decision to suspend the US Episcopal Church from decision-making, after the latter's clergy were allowed to perform same-sex marriages.