ことは確かである

it is certain that

→ こと
phrase Rare #42,110
it is certain that A formal expression used to assert that something is definitely true or will definitely happen. Often follows a plain-form clause.
JA: 彼女が約束を守ることは確かである。
EN: It is certain that she will keep her promise.

ジムその日家にいたことは確かである

It is certain that Jim was at home that day.

彼がその日家にいたことは確かである

It is certain that he was at home that day.

彼が生きているということは確かである

It is certain that he is alive.

ジョージが来ることは確かである

George is definitely coming.