The crucial difference between religion and science lies not in
what things they hold to be true, but in the
basis on which they decide which things to hold true. Science relies on evidence; religion relies on faith, meaning a willingness to believe things when there is no evidence that they are true. Science starts with the evidence and accepts whatever conclusion that evidence reveals; religion starts with the desired conclusion (God exists, Heaven exists), and then casts around for some basis for believing it. Science demands that evidence be objective and accessible to anyone -- its ideal tool is the controlled experiment, designed to test for only one variable, and described carefully enough that any other researcher can do the same experiment and see whether he gets the same result. Science knows that all humans, including scientists, have biases, and has developed procedures for filtering out such biases from its processes for assessing evidence. Religion embraces the unverifiable and the subjective -- its central claims (such as the existence of God) are generally formulated so as to be immune to objective testing. The religious believer debating an atheist, when his "arguments" for the existence of God are shot full of holes, will often fall back on what boils down to gut feeling and intuition. The same untestability which makes such "arguments" unanswerable also makes them useless as tools for discovering truth.
Due to its unique evidence-based approach, science has enabled us to create
technology, a vast array of tools that actually work, such as vaccines, computers, anesthetics, space probes, H-bombs, lasers, etc. No other supposed "way of knowing" has such a track record of creating things that verifiably work in the real world. Because of this, those groups of humans who have embraced science have acquired great power, not only over the natural world, but also (for good or for ill) over those groups of humans who have been less enthusiastic or less capable in adopting the scientific approach.
Because science and religion approach reality in such different ways, they inevitably come to different conclusions about almost any question which both of them take up. The differences about the age of the Earth, the origin of the human race, and so forth, are too well-known to need citing. So long as science is free to operate without interference from religion, these differences are not a practical problem for it. But when religion gains influence in politics, the results can be disastrous.
One of the best examples comes from Middle Eastern history. In the eighth century CE, Middle Eastern intellectuals discovered the philosophical heritage of Classical Greece and began translating it into Arabic. In the relatively tolerant climate of the time, the new ideas spread and a class of "philosophers" arose, promoting a skeptical and rationalistic approach to truth (as among the Greeks, the term "philosophy" was used in a broader sense than today, including scientific inquiry). Many Muslim rulers, themselves interested in the new thinking, downplayed its conflicts with theology in order to justify a policy of tolerance and even encouragement. Over the next three centuries a kind of scientific age arose, limited by modern standards but impressive for the time -- considerable advances were made in such fields as medicine, mathematics, and astronomy.
As Ibn Warraq has argued, this early so-called "Islamic civilization" was really a revival under Islamic rule of the advanced Hellenistic civilization which had dominated the Middle East and the eastern Mediterranean from the time of Alexander the Great's successors to the early Roman period.
There was continuous tension between philosophers and Islamic theologians, however, and around 1100 CE the conflict came to a head with the rise of the new school of Ash'arite theology. This school's leading proponent, the theologian al-Ghazâlî, attacked the views of the philosophers with devastating effect -- his writings (brilliantly argued, in their own way) wiped away the grey areas which had long enabled philosophers and rulers alike to maintain that there was no inherent conflict between Islam and Greek-inspired philosophy, and that one could thus embrace the latter while remaining a good Muslim. Since medieval Islam knew no separation of political authority from religion, the triumph of Ash'arite theology meant the end of the medieval Middle Eastern scientific age. Philosophers were persecuted and exiled, books were burned, inquiry was shut down, and in effect, an entire civilization lobotomized itself.
The decline of any civilization has multiple causes, but in the Islamic case, this self-imposed intellectual stagnation must have played a key role. Had science not been suppressed in the Middle East, for example, it might conceivably have gone on to develop more sophisticated weapons with which the Muslims could have fought off the devastating Mongol invasions a century later. Certainly several further centuries of development would have left the Middle East of the nineteenth century far better equipped to resist European colonialism. But that's not what
happened. Even today, in most of the Middle East, religion dominates government, law, and education to varying degrees. As a result no Muslim country is a leader in any field of science or technology, though several other non-Western countries are, notably Japan and South Korea (note that those countries are strongly secular).
The story of the rise of science in the West is the story of struggle
against reactionary religion. From Galileo to Darwin, discovery
after discovery was bitterly resisted in the name of religious dogma.
Even the twentieth century saw instances of "moral" objections to the
development of medicines to treat venereal disease, and religionists today are still fighting against stem-cell research and cloning. Even the embrace of
Lysenkoism by the Soviet state in the 1950s, which crippled the progress
of Soviet genetics, should also be counted as an example of this
problem -- Communism
has most of the essential characteristics of a religion,
and Stalin's insistence that truth be determined by consistency with
established dogma rather than by evidence perfectly mirrored the danger
which religion armed with state power has always presented to science.
It's astonishing that in the United States the threat still persists to some extent. The Republican party has become the party of religion in politics, leaving the Democrats by default as the party of secularism -- and this is the most fundamental divide between the two. We are fortunate in that our Constitution would make it difficult to create a real theocracy here. But the relentless Republican efforts to undermine science education (especially evolution), attack research that violates taboos, and give religious nonsense equal standing in official policy -- all this risks deepening the public's already abysmal ignorance of science and incomprehension of its value. The repressive social policy which is the chief focus of the
Christian Right's political activism would, if implemented, likely do even more to stunt the
country intellectually. Most creative people are not the sort that can
be happy living under a bunch of bronze-age taboos
written into law by scowling would-be ayatollahs. Many would leave,
taking the benefits of their creativity and innovation elsewhere.
The Ash'arites of modern America know this is the end-game for them. They know religion is in decline demographically and that this is their last chance to reassert their dominance and that of their medieval mentality in our society. I believe they will lose. But they will lose because we fight like hell against their influence.
