  Fortunately, the arguments from conflict do not work alone. Indeed,  they cannot, as the principle of non-opposition merely establishes a  constraint on successful psychological explanations. Appeals to this  principle can show where some division must exist, but they do not by themselves characterize the parts so divided. So, already in Book  Four’s arguments from conflict, Socrates invokes broader patterns of  psychology and appeals to the parts to explain these patterns (cf.  435d–436b).