Even though the popular picture of the scientific method shows a scientist building a hypothesis based on data from physical, 
not thought, experiments, Holton says Einstein was nevertheless using classic scientific method. "Hypotheses come from all kinds of directions. It depends very much on the particular skill of the person. Some, including Einstein, could visualize very well," and could interpret thought experiments quite effectively. Other types of scientists, he adds, "prefer their truth coming directly out of equations."
Although Einstein seemed to have a unique ability to peer inside the universe, Holton says he was also a great example to other scientists since he wrote about his experiences, philosophy and techniques. "This man allowed himself to be more public and frank, and in particular about his scientific method, which is very much the method still used by other physicists" (see "The Advancement of Science..." in the bibliography).
Although most of the great predictions growing from Einstein's work have finally been demonstrated, Holton points to one major exception: the "grand unified theory." Often called the holy grail of physics -- this single explanation would join all four physical forces under one umbrella.
For many years, electromagnetism, and the strong and weak nuclear forces have been explained by a single theory called the "standard model." Yet gravitation remains stubbornly outside the model, and that rankles physicists who think it must be concretely related to the other three forces.
Searching for the grand unified theory was something that Einstein, who died in 1955, "devoted 20 years of his life to," Holton says, but it still hasn't been found. Nevertheless, Holton, reflecting once more the physicists' preference for order, uniformity and simplicity, is confident that it will happen.
Summing it all up
If you've come this far and still feel you don't quite understand Einstein's ideas, you have good company. When the Nobel Committee awarded Einstein its prize in 1922, it honored his work in quantum mechanics and specifically excluded relativity.
And everybody makes mistakes. Einstein argued against the existence of black holes, which are now beyond dispute, and disliked the element of chance that underlies quantum theory, saying "God does not play dice with the universe." He also cooked up an unnecessary "cosmological constant" because his theories seemed to require a universe that was expanding or contracting -- a notion that seemed too weird. When observations by U.S. astronomer Edwin Hubble proved that the universe was expanding, he called the constant "the greatest blunder of his life."
But these are meaningless quibbles compared to achieving general relativity, which Thorne calls a kind of super-law of physics. Relativity is "not itself a law of physics," he writes, "but instead ... a pattern or rule which ... must be obeyed by all laws of physics, no matter whether they are laws governing electricity and magnetism, or atoms and molecules, or steam engines and sports cars."
Newtonian physics may still describe the stuff we see every day. But almost a century after a young patent clerk shouldered it aside with laws that apply to the whole universe, there's no question Einstein grasped the big picture. "All of our experience in the nearly 100 years since 1905 suggests that Einstein was right," Thorne maintains. "All new laws that have been successful in describing the real universe have turned out to obey Einstein's principle of relativity."
