A Scientist & Scientism
J.P. Moreland, in his book, Love God with all of your Mind writes about a time he met a believer in scientism:

When I extended my hand to Mr. Smith he started attacking Christianity without a moment's hesitation.

"I used to think that religion and philosophy were important, but now I recognize that they are just superstition," he asserted. "Science is the only area where we have knowledge. If you can quantify something or test it in the lab, then we can know it. Otherwise, it's just one person's opinion against another's. To me, the sole value of religion is that believing it helps some people who need that sort of thing, but religious beliefs are neither true nor rational because they are not scientifically testable."

I let him go on for what seemed like the longest ten minutes of my life. In the most gracious way I could muster, I finally got the chance to respond. "I have a few questions for you, Mr. Smith. I am puzzled as to how I should understand what you have asserted for the last ten minutes. You have not said one single sentence from science and nothing you have asserted is the least bit scientifically testable or quantifiable. In fact, you have spent all of your time making philosophical assertions about science and religion. Now, I get the distinct impression that you want me to take your ten-minute monologue as something that is both true and rational. But how can this be, given your scientism, because you do not believe that philosophical assertions are true or rational? On the other hand, if you don't think your own assertions are either true or rational, why have you been boring us with emotive expressions of autobiography for the last ten minutes? After all, some of the finger foods are getting cold."

My response must have shocked Mr. Smith because he literally muttered a few things under his breath and changed the subject. I wouldn't let him off the hook. "I have another question, Mr. Smith. As you know, there have been different definitions of truth offered by various thinkers. Can you give me one single scientific test that offers a definition of truth itself or that shows me that there is such a thing? I take truth to be a correspondence between a statement and the external world. If I say grass is green and, in fact, grass is green, my assertion is true. But what kind of scientific test will enable me to know what truth itself is or that we have it? What about the other assumptions of science? Can you give me a scientific proof that these assumptions are correct and reasonable to believe?

Before my very eyes, Mr. Smith's entire demeanor changed. He was accustomed to bullying Christians and it wasn't working now. The rest of the evening we were able to discuss the gospel and a number of related issues. I stayed in touch with Tom for the next year and not once during that time did Mr. Smith ever again attack Christianity at work.