Marx:

In their 1846 book The German Ideology, Marx and co-author Frederick Engels took a look at human history and made a plain but controversial observation. In any given historical period, the ideas that people generally think are the best and most important ideas are usually the ideas of the people in charge. If you have a lot of money and own a lot of property, then you have the power to propagandise your worldview and you have incentive to avoid appearing as if you're propagandising your worldview. Or, as Marx and Engels would put it: The ruling ideas of every epoch are the ideas of the ruling class.

Source: aljazeera.com