"To know the causes" means to understand the reasons or factors that lead to a certain outcome or result. It refers to gaining awareness or knowledge about the things that have caused a particular event or situation to happen. Full definition
Also, we don't know the cause of death. (theverge.com)
If they don't know the cause for the inflammation, then surgery will help but there's no guarantee that the inflammation would return again. (justarsenal.com)
It is the first study of its kind to look at two populations of animals with known causes of injuries. (carolinatails.org)