Truth and scepticism

When a social scientist, such as an economist or a sociologist, claims to have discovered a "natural law" of social behavior, it is common sense to say that the credibility of their theories depend on how well it describes the real world.
The real world is, off-course, all that we experience, all sort of empirical evidence.
It did happen that such "social scientists" were branded as genius because their theories were proved to be right through the observation of social events.
For example, the economist Milton Friedman claimed that the relationship between inflation (increase in price levels, increase in cost-of-living) and employment (more and more jobs) was wrong. A few years later, in the 1970s, parts of the world did experience both high unemployment rates and high inflation. The economist had become the new genius (the previous one was Keynes). Many analysts said that his theories correctly discribed "the truth".
However, a few years later, the relationship between inflation and employment came back and the controversy remains unsettled.
What does happen in economics also happens in politics. The neo-conservatives promoted the idea that the USA should be actively involved militarily "to help spread ideas of democracy and freedom". Their ideas did make sense for a while after September 11, then suddenly, these ideas look incredibly foolish under the light of Iraq's quagmire.
Throughout the history of the world, social conventions keep changing. Is there such things as "absolute truth" or "eternal truth"?

Sir Karl Popper (1902-1994) claimed that scientists had to "falsify" their own theories all the time so they can make the difference between what is completely wrong and what does seem to be true. As a matter of fact, almost all sorts of "truth" becomes one day challenged by some empirical evidence.
Whereas some "believers" may argue that such views are dangerous as "moral relativism", there is a much more positive way to describe "scepticism".
Scepticism is necessary as we can only experience a limited amount of events in a particular context at a particular point of time. Expecting our "believes" to be always true in any context for the next thousand years is not realistic.

It has long be held by anthropologists that moral standards are not the same in every societies.
It is equally true to say that there is an evolution in moral standards as time goes by.

However absolute scepticism is not a right way of thinking either (and definitely not a pragmatic one for decision-makers). There is one way to prove the wrongness of absolute scepticism. When a theory does apply to the real world in a certain context at a certain point of time, decision-makers take these theories as granted and apply them in their decisions. It's definitely wise to follow a "theory" as long as it is not proven to be wrong. If we deny decision-makers the ability to trust such "unfalsified" theories, then how can we expect that they make any decisions at all? What matters is to remain open-minded and accept counter-evidence even if we don't like it.