One, therefore, will give the definition of whatever he possesses the knowledge of; as one can by no means be acquainted with that which he cannot embrace and define in speech. And in consequence of ignorance of the definition, the result is, that many disputes and deceptions arise. For if he that knows the thing has the knowledge of it in his mind, and can explain by words what he conceives; and if the explanation of the thought is definition; then he that knows the thing must of necessity be able also to give the definition.