foregone conclusion, a

1

An outcome regarded as inevitable, as in The victory was a foregone conclusion.

2

A conclusion formed in advance of argument or consideration, as in The jury was warned to consider all of the evidence and not base their decision on a foregone conclusion. This idiom probably was invented by Shakespeare (Othello, 3:3) but scholars are not agreed as to his precise meaning. [c. 1600]

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.