What it means
ないものでもない expresses that something is not entirely impossible or that the speaker cannot completely rule it out. It presents a possibility cautiously and often conveys deliberate understatement rather than firm approval or certainty. The construction commonly follows a verb in its negative form and is used in formal discussions, writing, and careful statements.
Usage note
This construction is weaker and more indirect than a direct statement that something is possible. Its double-negative form can also make the speaker sound reserved, so it should not be interpreted as an enthusiastic or definite acceptance.
How to use it
その提案を受け入れられないものでもありません。
It is not entirely impossible to accept that proposal.
その提案を受け入れられないものでもない。
It is not entirely impossible to accept that proposal.