A subject with two or more parts is said to be compound. If the parts are connected by and, the subject is nearly always plural.
Ability and desire is a plural subject, so its verb should be have.
EXCEPTIONS:When the parts of the subject form a single unit or refer to the same person or thing, treat the subject as singular.
When a compound subject is preceded by each or every, treat the subject as singular.
This exception does not apply when a compound subject is followed by each:
Subject-verb agreement at a glance
When to use the -s (or -es) form of a present-tense verb
Exercises:
Subject-verb agreement 1
Subject-verb agreement 2
Subject-verb agreement 3
Subject-verb agreement 4
Related topic:
Pronoun-antecedent agreement with compound antecedents