Cultural accumulation changes what we are and what we do from one generation to the next and, as far as scientific knowledge is concerned, changes occur so quickly that we tend to imagine them as distant theories or very recent developments.
A heated debate exists on the subject of Big Data. What can be expected and what not from them? Do data speak for themselves?
How do decision-making processes affect brain activity? What role do emotions play on finances?
In the vernacular, theory amounts to opinion. Everyone has theories. But in science, a theory is a verified body of knowledge.