Contrary to popular belief, when scientists use the word "theory", they are not referring to conjectures that they have
pulled out of thin air and have no data to support such claims. The scientific use of the word "theory" is much different than the colloquial use.
In science, a theory refers to an integrated set of principles that explain and predict events that are observed in the natural world. Theories, in the scientific sense, summarize and explain facts, and imply testable predictions that allow for the falsification of the theory. Theory is vital to scientific endeavour, as it generates hypotheses to be tested, gives direction to research (and even suggests new areas
for research), and, if the theory is good, has a high amount of explanatory power without requiring extensive modification to the theory. Theory without data is just
conjecture, but data without a theoretical explanation is as good as meaningless to scientific practice.