Hence, it is invalid. So, as previously explained, knowing that the premises of an argument are true is not sufficient evidence to establish the validity of an argument. All ontologists are logicians. So, all metaphysicians are logicians. Be sure to include the argument form, substitution instance, and a brief explanation as to why the substitution instance provided may properly be called a counterexample.
All orange trees are plants.
All orange trees are trees. All plants are trees. The substitution instance provided may properly be called a counterexample to the argument form, since it contains obviously true premises and an obviously false conclusion. Moreover, the substitution instance follows the proper argument form. At least one person does not love logic.