There are some people born blind and deaf. They never see anything and never hear anything, and yet they still can learn that sound and sight exist without personally experiencing "evidence" in the way a seeing and hearing person does.
Jesus taught through illustrations for a reason.
The Bible says there would be a new covenant with laws written on hearts.
The heart of a person is in a place you and I cannot see. We can only see what comes out of the heart through a person's mouth or action.