I think it should be "philosopher", but I am not sure.
Does philosophy encompass all subject matter?
Is there a word that describes someone who studies all subjects?
So, if a scientist studies science, and a theologian studies religion, is there a word for someone who studies both?
A sample sentence might be:
The '_____' is constantly learning, because the universe is infinite.
Here is an analogy:
Science is to Scientist as Everything is to '_____'.
Edit:
The word is likely to end with -ist or -er. The word should describe a person who specifically studies everything. My made up word would be: "everythingologist".