(Latin: omnis, all; scire, to know)
God knows all things simply and absolutely.
He, first of all, adequately knows His own essence and fully comprehends it in all its infinity, and He alone so comprehends it.
Further He knows all things outside of Himself, all His creatures and everything that concerns them, whether these things be past, present or future.
Nor is this knowledge like ours, successive in its operation.
In God there is no successsion of acts, all is present to Him always, the past as well as the future, everything is as if it were happening now, nor is there anything in all the world which is not present to Him always.
New Catholic Dictionary