One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike. We still do not know one thousandth of one percent of what nature has revealed to us. It is entirely possible that behind the perception of our senses, worlds are hidden of which we are unaware.
Albert Einstein's desk on the day of his death, April 18th, 1955. The renowned theoretical physicist was working on a unified theory, a single elegant theory to combine gravity and electromagnetism. He was motivated by an intellectual need to unify the forces of nature. More so, he felt strongly that all of nature must be described by a single theory. During his Nobel lecture in 1923, Gothenburg, Sweden he commented;
"The intellectual seeking after an integrated theory cannot rest content with the assumption that there exist two distinct fields totally independent of each other by their nature."