Determine whether the given argument is valid:

If Socrates was a philosopher, then he wasn’t a historian.
Socrates was a historian.
So Socrates was not a philosopher.

An argument is valid if and only if its conclusion is entailed from its premises,

A valid argument is not necessarily sound. That is, the premises do not need to be true.

Hence you only need to examine the form of the argument, not the soundness of the premise.

The form is as follows:

P1: (S in P) implies (S not in H)
P2: S in H
C: S not in P

Is this form valid?