there's no knowing/saying/telling...

(there's) no knowing

There is no way one can be sure; no one knows or can tell. He's already very volatile at the moment—no knowing how he'll react to bad news like this. Unfortunately, there's no knowing if such an effort will actually translate to a meaningful, long-lasting improvement in the economy.
See also: knowing, no

(there's) no saying

There is no way one can be sure; no one knows or can tell. He's already very volatile at the moment—no saying how he'll react to bad news like this. Unfortunately, there's no saying if such an effort will actually translate to a meaningful, long-lasting improvement in the economy.
See also: no, saying

(there's) no telling

There is no way one can be sure; no one knows or can tell. He's already very volatile at the moment—no telling how he'll react to bad news like this. Unfortunately, there's no telling if such an effort will actually translate to a meaningful, long-lasting improvement in the economy.
See also: no, telling
Farlex Dictionary of Idioms.

there’s no ˈknowing/ˈsaying/ˈtelling...

it is impossible to know/say/tell: There is no telling what he may do when he gets angry. There’s no saying what will happen.
See also: knowing, no, saying
Farlex Partner Idioms Dictionary
See also:
  • drive (one) out of office
  • force (one) out of office
  • force out of office
  • give (one) (one's) head
  • give head
  • give somebody their head
  • give someone their head
  • cooking for one
  • 1FTR
  • as one door closes, another (one) opens