In any science experiment, you take a situation, change something about it, and measure the effect of your action on the situation. When you're a kid, you might start with a still cup of vinegar, add baking soda, and be delighted when the vinegar bubbles over. In the science of mind, you can experiment with adding new thoughts to your situation, and you can see measurable results.
We are slightly more balanced today, but in the early 20th century, it would be fair to say that people worshipped science. It seemed to offer predictability and reliability to a chaotic world. It offered new technologies that seemed to give us conveniences and greater control over our lives. Science was the new religion, and has remained the religion of choice for some people.
So in the 1920s and 30s, if you wanted to get your message across effectively, you delivered that message in terms of its scientific aspects. Many Christians and other spiritual folk discovered spiritual tools that worked predictably and reliably, but they lived in a world that was skeptical of spiritual healing, even among religious people. So they spoke of their discoveries in terms of science. They called their philosophies Scientific Christianity, Divine Science, and Science of Mind. Even the church called Unity spoke of "scientific Christian practice."
The phrase "science of mind" came into use on a broad scale after Ernest Holmes wrote a book by that title in 1926. He revised it completely in 1938, and the book became a classic. It is still the basic text for the United Churches of Religious Science. For over 75 years, this church has also published a magazine called "Science of Mind." Its purpose, like that of all such literature, is to help you change your life by changing your thinking.
The basic premise of the science of mind - of the whole New Thought movement - is a deep belief that there is a Spirit in all humans and that Spirit is God. As we learn to think, speak, and act as if this were true, our lives show measurable results of our changed attitudes and beliefs. Our physical and mental health improves. We enjoy peaceful sleep and joyful awakenings. Our relationships are happier. We have the wisdom to handle challenging situations with grace and ease. We consistently have everything we need, when we need it.
Fast-forward almost a century, and you see that the science of mind has undergone something of a revival. While it has always remained strong in business and success literature (with the religious language taken out), the science of religion had come to seem cultist, or at least quaint, in the minds of people in mainstream religious life. For people who were not religious, to know that something works was not enough; they wanted to know why it worked.
Now, people in the mainstream have begun to learn about quantum mechanics. The work being done in quantum physics literally shows us the "mechanics" of how the mind works. Suddenly, the people who were once written off as quaint or as cult figures enjoy a new respect. Their writings have become timely again, whether you are of a religious or a scientific bent. As the mainstream become more educated about these discoveries, it will make more sense to them to speak of a science of mind.