And it was he that first gripped another cub by the ear and pulled and tugged and growled through jaws tight-clenched.

And certainly it was he that caused the mother the most trouble in keeping her litter from the mouth of the cave.
The fascination of the light for the grey cub increased from day to day.
He was perpetually departing on yard-long adventures toward the cave's entrance, and as perpetually being driven back.

Only he did not know it for an entrance.

He did not know anything about entrances--passages whereby one goes from one place to another place.

He did not know any other place, much less of a way to get there.