>> There was a debate about whether light was a wave or a particle -- evidence supported both views. > Not before the 20th century, Yes before the 20th centur

>> There was a debate about whether light was a wave or a particle -- evidence supported both views. > Not before the 20th century, Yes before the 20th century. I refer you to the debate between Newton and Huygens as well as Hooke, his contemporaries with respect to these ideas. http://www.studyphysics.ca/newnotes/20/unit04_light/chp1719_light/lesson57.htm http://www.studyphysics.ca/newnotes/20/unit04_light/chp1719_... Such debates persisted from then until the shaping of quantum theory.