it can't be helped; there is no choice; inevitable
A somewhat formal or literary set phrase expressing resignation or acceptance of an unavoidable situation. Similar in meaning to 仕方がない but with a more classical, weighty tone.
If it comes to war, it can't be helped.
There is no choice; let us accept our fate.
Also formal, but focuses on the lack of alternatives due to circumstances, while 是非もなし emphasizes the inevitability of the outcome itself.
Standard kanji spelling for this set phrase.
Alternate kanji spelling using 無し instead of なし; less common but still seen.
From 是非 (right and wrong; by extension, the pros and cons or the way things are) + も (inclusive particle) + なし (classical negative of ある, 'not exist'). Literally 'there is no right or wrong about it', i.e., the matter is beyond debate or choice.