Collocations for supposition - noun

reasonable
It is a reasonable supposition that many mothers would welcome the offer of part-time work.

mere, pure (both esp. BrE)
That is mere supposition!

make
We can make a supposition about how the accident happened.

be based on
confirm, support

be correct, be wrong
be based on sth

on (a/the) supposition
She was charged on the supposition that she had colluded with her husband in the murders.

supposition about
They are making all sorts of suppositions about our possible reaction.

supposition of
a supposition of innocence