Evolutionary convergence occurs when, for example, nature winds up with at same solution from two different directions. Like how every planet in Star Trek is populated by white people with prosthetics stuck to their foreheads.
The dolphin and the ichthyosaur is probably a better example:
But ideas can also converge. For example:
"When the existence of the church is threatened, she is released from the commandments of morality. With unity as the end, the use of every means is sanctified, even cunning, treachery, violence, simony, prison, and death. For all order is for the sake of the community, and the individual must be sacrificed for the common good."
- Dietrich von Nieheim, Bishop of Verden, De Schismate Libri III, AD 1411.
"To us, everything is permitted, because we were the first in creation to take up the sword not for the purpose of enslavement and repression but in the name of universal liberty and emancipation."
- Krasny Mech (Red Sword) Bulletin, Kiev Cheka (Extraordinary Commission for Combating Counter-Revolution and Sabotage, Soviet Secret Police), regarding massacre of peasant uprising, AD 1920.
Some things never change.
Note the first quote is cited from Darkness at Noon by Arthur Koestler, an anti-communist, apparently from a paraphrase by Ludwig von Pastor in History of the Popes (1906), extrapolated from a more meandering original statement by Nieheim on dealing with the Antipopes in De Modis. Of course, paraphrasing quotes kind of defeats the purpose. But then, that's what translations often amount to. The underlying point is the same but Pastor seems to have added a more poetic edge to it.
A relevant section from De Modis:
"Then, if the Church will not be able to accomplish it in this way, then by way of deceit, fraud, arms, violence, power, promises, gifts and money, and finally, prison and death, it is appropriate to procure in any way whatever the most holy union and conjoining of the Church." - Dietrich von Niehem
As Stephen Pinker notes in Angels of Our Better Nature, more violence and murder has been carried out in the name of morality than has ever been committed for the sake of sin.
Rebel Angels delves into the divide between righteous revolutionary theory and reality.
