When I read essays from Eliot, I find him using "that which" frequently, e.g.
- the combination which is the murder of Agamemnon is probably as complex as that which is the voyage of Ulysses.
- A very small part of acting is that which takes place on the stage!
- They belong to a different race. Their crudity is that which was of the Roman, as compared with the Greek, in real life.
I can kind of guess its usage, but I want to know more about this grammar structure. Searching on Google mostly gave me the simple difference between "that" and "which", and some examples using "that which":
- that which we call a rose (from "Romeo and Juliet")
- that which we persist in doing
It is a pity that Google search does not direct me to any useful page about "that which". Can someone explicate its grammar for me?