String theory seems to violate the rule of simplicity. In science, one goal is to propose the fewest “entities” or rules needed to explain how something works. In many ways, the history of science is seen as a progression of simplifying the complex array of natural laws into fewer and fewer fundamental laws.

Take Occam’s razor, which is a principle developed in the 14th century by Franciscan friar and logician William of Occam. His “law of parsimony” is basically translated (from Latin) as “entities must not be multiplied beyond necessity.” (In other words, keep it simple.)

Albert Einstein famously stated a similar rule as “Make everything as simple as possible, but not simpler.” Though not a scientific law itself, Occam’s razor tends to guide how scientists formulate their theories.

In some ways, string theory seems to violate Occam’s razor. For example, in order for string theory to work, it requires the addition of a lot of odd components, such as extra dimensions and new particles, which scientists haven’t actually observed yet. However, if these components are indeed necessary, then string theory is in accord with Occam’s razor.

Some people believe that science is purely objective. And, of course, science is objective in the sense that anyone can apply the principles of science in the same way and get the same results. But the idea that scientists are themselves inherently objective is a nice thought, but it’s about as true as the notion of pure objectivity in journalism.

The debate over string theory demonstrates that the discussion isn’t always purely objective. At its core, the debate is over different opinions about how to view science.

In truth, scientists make choices continually that are subjective, such as which questions to pursue. For example, when string theory founder Leonard Susskind met Nobel Prize winner Murray Gell-Mann, Gell-Mann laughed at the very idea of vibrating strings. Two years later, Gell-Mann wanted to hear more about it.

In other words, physicists are people. They have learned a difficult discipline, but this doesn’t make them infallible or immune to pride, passion, or any other human foible. The motivation for their decisions may be financial, aesthetic, personal, or any other reason that influences human decisions.

The degree to which a scientist relies on theory versus experiment in guiding his activities is another subjective choice. Einstein, for example, spoke of the ways in which only the “free inventions of the mind” (pure physical principles, conceived in the mind and aided by the precise application of mathematics) could be used to perceive the deeper truths of nature in ways that pure experiment never could.

Of course, had experiments never confirmed his “free inventions,” it’s unlikely that anyone would be citing him a century later.