**Conjecture**Let and are filters on a set and . Then

See here for some equivalent reformulations of this problem.

This problem (in fact, a little more general version of a problem equivalent to this problem) was solved by the problem author. See here for the solution.

Maybe this problem should be moved to "second-tier" because its solution is simple.

## Bibliography

*Victor Porton. Open problem: co-separability of filter objects

* indicates original appearance(s) of problem.