Learn Italian: Se il ragazzo è responsabile, gli lasciamo usare la macchina. - If the boy is responsible, we let him use the car.

This is a tricky rule for the lasciare + infinitive structure. Because the second verb (usare) has its own direct object (la macchina), the person receiving permission becomes the indirect object (gli). If the second verb didn't have a direct object, like in 'we let him sleep,' you would use the direct object pronoun lo (lo lasciamo dormire).

Why isn't there a preposition like a or di between lasciamo and usare?

When lasciare means 'to let' or 'to allow,' it is followed directly by an infinitive verb, without any preposition in between. It behaves a lot like modal verbs such as potere or volere.

In English we say 'let him use', putting 'him' in the middle. Can I say lasciamo lui usare?

No, Italian keeps the conjugated verb and the infinitive together. The pronoun for the person being allowed must either go before the conjugated verb (gli lasciamo usare) or, if you really want to emphasize 'him,' at the end as an indirect object (lasciamo usare la macchina a lui).

Why does the Italian sentence use the present tense for the 'if' clause (se il ragazzo è) instead of the future tense?