  In this short viewpoint, we discuss the assignment of ionic charges in
solids. We argue that formal oxidation states serve a useful function, and that
absolute values of partial charges should be interpreted and applied with
caution; the charge assigned can never be definitive and depends on the type of
property studied and the type of analysis performed. Careful analysis can be
used to avoid unphysical conclusions such as a recent report on the Ti(III)
nature of Ti in stoichiometric TiO$_2$.
