If you agree with something in principle, you agree in general terms to the idea of it, although you do not yet know the details or know if it will be possible.

Do you agree in principle or principal?

Principal is a noun and adjective with specialized meanings in finance and law but most commonly used to refer to someone in a position of authority or high prominence. Principle is only a noun and refers to a natural, moral, legal rule or standard.

How do you use principle in a sentence?

1. Her idea is sound in principle. 2. In principle I agree with the idea, but in practice it's not always possible.