3.55 speaker's decisions on transitivity

There are not many verbs which are always transitive or always intransitive. The decision about whether or not to mention an object is left to the users. If they think that the people reading or listening to them will have no difficulty in working out what person or thing is affected by the action, then they can leave out the object. If they think that this will not be clear, they will use an object in order to prevent misunderstanding. The main reasons for omitting the object are that it is obvious from the meaning of the verb itself, or that it is obvious from what has already been said.