Physicist Ian Hutchinson offers an insightful metaphor for the current controversies:
“The health of science is in fact jeopardized by scientism, not promoted by it. At the very least, scientism provokes a defensive, immunological, aggressive response from other intellectual communities, in return for its own arrogance and intellectual bullyism. It taints science itself by association.”
So if science is distinct from scientism, what is it? Science is an activity that seeks to explore the natural world using well-established, clearly-delineated methods. Given the complexity of the universe, from the very big to very small, from inorganic to organic, there is a vast array of scientific disciplines, each with its own specific techniques. The number of different specializations is constantly increasing, leading to more questions and areas of exploration than ever before. Science expands our understanding, rather than limiting it.
Scientism, on the other hand, is a speculative worldview about the ultimate reality of the universe and its meaning. Despite the fact that there are millions of species on our planet, scientism focuses an inordinate amount of its attention on human behavior and beliefs. Rather than working within carefully constructed boundaries and methodologies established by researchers, it broadly generalizes entire fields of academic expertise and dismisses many of them as inferior. With scientism, you will regularly hear explanations that rely on words like “merely”, “only”, “simply”, or “nothing more than”. Scientism restricts human inquiry.
Source: Thomas Burnett, What is Scientism? on the AAAS website