In A Wrinkle in Time, what is the thing and which historical figures have opposed it? Chapter 5

The Black Thing is the embodiment of evil.  Evil is often
described as "dark" or "black" in literature.  The Black Thing has been opposed by great
artists, religious figures, inventors, philanthropists and thinkers throughout Earth's
history.  Basically, the Black Thing is a Devil-like character battled by Christ and
other religious figures, because the novel references Biblical versus.  Buddha is also
mentioned.  It was also fought by other important thinkers.  Leonardo da Vinci,
Shakespeare, Einstein, Bach, and Gandhi are also
mentioned.

By describing the Black Thing as having been so
important to various historical figures, L’Engle is establishing the common thread of
humanity that fights with evil.  It is not just religion that is important to battling
evil and establishing good, but also art, science, philosophy and good
works.