But knowing the evolution is very helpful to me. When you
  consider the relationship of the behavior of electrons and
  "electron holes" in semiconductors and compare it to aligning
  magnetic fields... it really helps in comprehending "how it
  works" from several different viewpoints. electrons and electron
  holes analogize to balls in cups moving around and aligning
  magnetic fields analogizes to changing water flow direction. Yet
  even within semiconductor lingo, the "source/drain" metaphor
  remains.* Whole thing is fascinating honestly.