Thinking Theoretically 73By testing groups of interrelated hypotheses, theories are either refuted or supported
and refined— but never conclusively “proven”— and new relationships are found that
demand subsequent testing.
A famous example of a power ful theory from the natu ral sciences is Charles Dar-
win’s theory of evolution. Darwin’s theory of natu ral se lection and his concept of
survival of the fittest explain what had previously been puzzling variation in the col-
oration and beak shapes of identical species of birds in dif er ent environments. We
say that Darwin’s theory is power ful because it has survived many challenges; its logic
is consistent, even with evidence unavailable to Darwin at the time he formulated his
theory. The theory is therefore very general in the sense that it can explain seemingly
unique variations across space and time. Yet in neither natu ral nor social sciences
do we ever consider theories to be “proven” or “settled” or “fact.” Theories, whether
Darwin’s or Albert Einstein’s or Kenneth Waltz’s, can always be overturned or
refuted by new evidence or better theory. Theories are therefore not explanations that
scientists “believe in.” Rather, we say they are stronger or weaker, or more or less
supported.
Moving from description to explanation to theory, and from theory to testable
hypotheses, is not an entirely linear pro cess. Although theory depends on a logical
The destruction of a statue of Saddam Hussein in Baghdad became a symbol of his regime’s
defeat in 2003 by a U.S.- led co ali tion. Theory can help us understand why Saddam risked war
with a more power ful country and why the United States chose to invade Iraq.