Final answer:
The sentences exemplify the use of indefinite and definite descriptions and their respective denotations. Indefinite descriptions, like 'a dog' and 'a man', do not denote specific objects. Definite descriptions, like 'the current King of France', can refer to non-existent objects but do not denote them.
Step-by-step explanation:
In the sentence 'If I had a dog, I would walk it', 'a dog' is an indefinite description, meaning it refers to any dog that might fit the description. It does not denote a specific dog because the sentence is talking about a hypothetical situation. The pronoun 'it' is used to refer back to the noun 'dog', which is the antecedent of 'it'. In this case, 'it' does not denote a specific dog either because the sentence is talking about a hypothetical situation. In the sentence 'I need a man', 'a man' is also an indefinite description, referring to any man who might fit the description. Like in the previous example, it does not denote a specific man.