 This sentence contains the definite NP “his son”, which in its turn contains the pronoun “his”, and the focus particle “too”. Assuming the pronoun’s antecedent is “Fred”, the definite NP triggers the presupposition that Fred has a son, while the focus particle triggers the presupposition that someone other than Fred’s son is protesting. Note that in this example the presupposition triggered by the definite NP is “inherited” by the sentence as a whole, while the one triggered by “too” is not: normally speaking, an utterance of (43) would license the inference that (according to the speaker) Fred has a son, but not that someone else besides Fred’s son is protesting.