There are things we used to know. 
When I say we, I don't necessarily mean me and you. I am intending this in the larger sense of us, as a people. The people of our community, of our area, of our country. This means that when I additionally say used to know, I am talking about something that our ancestors knew and we no longer know.
One of the many sources of my assessment of our lack of knowledge and our ancestors actual knowledge is in the textbooks that they would give to their children. The number one textbook that was given to children in this country is The New England Primer. This textbook was the number one selling book in the American colonies and eventually in these United States. It was based on an older Primary School Textbook from England, which means ... to put this bluntly... it was around for a really long time. It was literally around - and used - for generations. It was used, until it was replaced by men like Horace Mann. 
In the very center of this children's reader was the Westminster Shorter Catechism. Here is a screenshot of that page in the Primer. (And yes, sometimes their "s" will look like an "f".)