There are two common mistakes. One mistake is to claim that science and religion are in eternal conflict or in a state of war. The other mistake is to claim that science and religion are different but complementary, as if both are needed to achieve a complete sense of truth.
In the 1870s, as science was becoming professionalized, a few prominent people starting arguing that science and religion were at war. They even fabricated a historical narrative. Most of us have been told that people in the Middle Ages believed the earth was flat and Columbus was warned that he would sail off the edge of the world. This is nonsense. People have known that the earth is spherical since at least the 5th century BC. The idea that medieval people believed in a flat earth was fabricated to discredit religious people in the context of late-19th-century Darwinian debates.
In terms of systems theory, the creation of the flat-earth myth was about separating science and religion. Proponents of science wanted to discredit religion, arguing that science and religion are incompatible and that religious believers are so stupid they believe the earth is flat. This is known as the conflict thesis.
According to systems theory, science and religion are different function systems; however, they do not have to be in conflict; they might just ignore each other. The two discourses are not fighting over the same territory. Science seeks truth or a sense of order or intellectual structure—predictability rather than randomness; it wants to understand causes and effects and how to change things in orderly ways. Religion seeks something else—a sense of the transcendent or a causeless reality, something outside ordinary human experience. For instance, religion also offers a narrative for what happens after death or even before birth, as in ideas of reincarnation. Many people also claim that religion is necessary because it provides a moral code, but this is not true—more on this later.
Religion has many functions, such as helping people, with the aid of rituals, to deal with or find meaning in crises or transitional phases—e.g., birth, death, illness, puberty, marriage, etc. It can also give meaning to seasonal changes, as in Easter, winter solstice rituals, etc.
Religion is very complex, and religion as a concept is an oversimplification invented by scholars. We might say, following Luhmann, that religion is a form of communication that draws a distinction between immanence and transcendence, but this is also a simplification. There may not be a single distinction that covers religion or religious communication. Ultimately, religion is just a word that facilitates communication. The same might be said for science.
The mistake people inevitably make (the second mistake mentioned above) is to assert that science and religion are somehow complementary, as if putting them together gives a more comprehensive view. But these arguments want to somehow unify science and religion, which is not at all necessary. Science and religion do not need each other; each can go its own way without even taking notice of the other.
Albert Einstein made this mistake when said, “Religion without science is blind. Science without religion is lame.” The truth is that science and religion can do just fine without one another.
Nor does religion have to conflict or compete with ethics if religion assumes an antinomian stance, the idea that salvation comes through grace alone and has nothing to do with following a moral code or law. Ethics can remain within the realm of philosophy if religion ignores ethics and morality.