[LAC-Tech]

I think it's pretty clear to me. Puritan aligned forces overthrew the English Monarchy and established a republic - some 150 years later left and right came about when opponents of the French monarchy would sit on the left. There's also a very clear relationship between Puritans and the Whigs - it's surely very clear that they were to the left of the Tories.

In either century, the right represents old moral values, and the left represents a fresh new source of moral values which seek to replace the old. Granted, in the 17th century those new moral sources were religious and in the 21st century they are secular - the substance of what is now left and what was then left has absolutely changed. But the overall structure is the same.