'Know' in the Bible

And they said every one to his fellow, Come, and let us cast lots, that we may know for whose cause this evil is upon us. So they cast lots, and the lot fell upon Jonah.

And he said unto them, Take me up, and cast me forth into the sea; so shall the sea be calm unto you: for I know that for my sake this great tempest is upon you.

So why shouldn't I be concerned about Nineveh, that great city, in which there are more than 120,000 human beings who do not know their right hand from their left, as well as a lot of livestock?