I am reminded that in Europe, historians like myself characterize their research and writing as “scientific”. I have stayed away from this characterization myself, feeling that “science” is the field of biology and physics.
As someone who was trained as a research scientist, I agree with her. The scientific method requires that the researcher looks at what is happening in the real world, develops a(n) hypothesis or a set of hypotheses about why it is happening and sets up controlled experiments to test whether or not the hypotheses are correct. There is no way that historians can do this. They can’t say “we think the causes of WWII were X, Y and Z” and then go back to the 1930s and change the conditions to see if WWII still happens without X or without Y. Much psychological and sociological research also follows the scientific method, although it is sometimes difficult to control as many of the circumstances as researchers would like because research ethics committees won’t allow some things to be done or not done on human beings (and with good reason).
Good historians are careful, methodical investigators, but they are not scientists because they have no way of controlling the circumstances they are investigating in order to test their hypotheses. The more contemporary the history being written, the better able the historian is to take into consideration context and various biases in their analysis of the material available to them, but they still can’t change the events of the past. Historians of early Christianity and the various other things that come under the heading “Ancient History” can only work with the texts available, knowing that in some situations this gives them access to incredibly skewed data. Their analysis can still tell us some very valuable things, but it is not science.