Document ID: ./input/supremecourt_opinions/opinions/19pdf/17-1618_hfci.pdf
Page Number: 9

Cite as:  590 U. S. ____ (2020) 

5 

Opinion of the Court 

A 

The  only  statutorily  protected  characteristic  at  issue  in 
today’s cases is “sex”—and that is also the primary term in
Title VII whose meaning the parties dispute.  Appealing to
roughly  contemporaneous  dictionaries,  the  employers  say 
that, as used here, the term “sex” in 1964 referred to “status 
as  either  male  or  female  [as]  determined  by  reproductive
biology.”  The employees counter by submitting that, even
in 1964, the term bore a broader scope, capturing more than
anatomy and reaching at least some norms concerning gen-
der identity and sexual orientation.  But because nothing in
our approach to these cases turns on the outcome of the par-
ties’ debate, and because the employees concede the point
for  argument’s  sake,  we  proceed  on  the  assumption  that 
“sex” signified what the employers suggest, referring only 
to biological distinctions between male and female.

Still, that’s just a starting point.  The question isn’t just
what “sex” meant, but what Title VII says about it.  Most 
notably,  the  statute  prohibits  employers  from  taking  cer-
tain actions “because of ” sex.  And, as this Court has previ-
ously explained, “the ordinary meaning of ‘because of ’ is ‘by
reason of ’ or ‘on account of.’ ”  University of Tex. Southwest-
ern Medical Center v. Nassar, 570 U. S. 338, 350 (2013) (cit-
ing Gross v. FBL Financial Services, Inc., 557 U. S. 167, 176 
(2009);  quotation  altered).  In  the  language  of  law,  this
means  that  Title  VII’s  “because  of ”  test  incorporates  the 
“ ‘simple’ ”  and  “traditional”  standard  of  but-for  causation. 
Nassar, 570 U. S., at  346, 360.  That form  of causation is 
established whenever a particular outcome would not have
happened  “but  for”  the  purported  cause.  See  Gross,  557 
U. S.,  at  176.    In  other  words,  a  but-for  test  directs  us  to 
change one thing at a time and see if the outcome changes.
If it does, we have found a but-for cause. 

This  can  be  a  sweeping  standard.  Often,  events  have 
multiple but-for causes.  So, for example, if a car accident