String theory is at the cutting edge of science. It’s a mathematical theory of nature that, at present, makes few predictions that are testable. This begs the question of what it takes for a theory to be scientific.

Before you can figure out whether string theory is scientific, you have to ask, “What is science?”

Science is the methodical practice of trying to understand and predict the consequences of natural phenomena. This is done through two distinct but closely related means: theory and experiment.

Not all science is created equal. Some science is performed with diagrams and mathematical equations. Other science is performed with costly experimental apparatus. Still other forms of science, while also costly, involve observing distant galaxies for clues to the mystery of the universe.

String theory has spent more than 30 years focusing on the theory side of the scientific equation and, sadly, is lacking on the experimental side, as critics never hesitate to point out. Ideally, the theories developed would eventually be validated by experimental evidence.

Most people are taught in school that science follows nice, simple rules called the scientific method. These rules are a classical model of scientific investigation based on principles of reductionism and inductive logic. In other words, you take observations, break them down (the reductionism part), and use them to create generalized laws (the inductive logic part).

• Observe a phenomenon: Look at nature

• Test the hypothesis: Perform an experiment

• Analyze the data: Confirm or reject the hypothesis

String theory’s history certainly doesn’t follow this nice classical model.

Turns out there’s no single scientific method that all scientists follow. Scientists don’t look at a list and think, “Well, I’ve observed my phenomenon for the day. Time to formulate my hypothesis.” Instead, science is a dynamic activity that involves a continuous, active analysis of the world. It’s an interplay between the world we observe and the world we conceptualize.

Science is a translation between observations, experimental evidence, and the hypotheses and theoretical frameworks that are built to explain and expand on those observations.

Still, the basic ideas of the scientific method do tend to hold. They aren’t so much hard and fast rules, but they’re guiding principles that can be combined in different ways depending on what’s being studied.

The ideas of the scientific method are often traced back to Sir Francis Bacon’s 1620 book Novum Organum. It proposed that reductionism and inductive reasoning could be used to arrive at fundamental truths about the causes of natural events.

In the Baconian model, the scientist breaks natural phenomena down into component parts that are then compared to other components based on common themes. These reduced categories are then analyzed using principles of inductive reasoning.

Inductive reasoning is a logical system of analysis where you start with specific true statements and work to create generalized laws, which would apply to all situations, by finding commonalities between the observed truths.