theorizer

/ˈθiːəraɪzər/
noun
  1. A person who forms or suggests ideas or explanations about how something works, often without having solid proof.
    • He was known as a great theorizer, but his ideas were hard to test in real experiments.
    • As a theorizer, she spent most of her time thinking about the origins of the universe.
    • The theorizer proposed a new way to understand how children learn languages.