Should it be "has" or "have"?

[Brahman]

I found the following sentences in a book:

"Let the world have its own ways. Mind your own affairs".

I thought it should have been "Let the world has its own ways...". But my friend felt that it is correct as is. (When I re-read the sentence, I felt that my friend could be right). However, neither of us can explain the reason for our choices. Can you please help us?

[Alan]

Of course 'have' is correct: the infinitive form is required here.