v. To assume some truth without proof, usually for the purpose of reaching a conclusion based on that truth.
the GNU version of the Collaborative International Dictionary of English
v. To suppose beforehand; to imply as antecedent; to take for granted; to assume.
The Century Dictionary and Cyclopedia
To suppose beforehand; take for granted in advance of actual knowledge or experience.
To assume beforehand; require or imply as an antecedent condition; necessitate the prior assumption of.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
v. require as a necessary antecedent or precondition
v. take for granted or as a given; suppose beforehand
Word Usage
"That said, such calls presuppose that Obama will be included in the "need to know" loop of any hardcore evidence of aliens contact ... and I very much doubt he will."