R is for reality, whether or not it exists.
In science, you are asked to look at the world around you, make observation about how the world works, and use math as a way to reason out predictions. But, what if our observations on the world around us are unreliable? We rely on our senses to relay information to us, but we can often fool the senses and the brain. Our sense are not infallible. Look at the classic "rubber hand illusion" and observe how our sense of body ownership can be tricked. Illusions and magic tricks have amazed us for centuries. What I'm trying to say is can you trust own observation of the world. How can we trust ourselves? We can compare these ideas to the observation of others, and build a view of the world from that. In a way this may work, because as one person we can only see one part of life, but others will also give us more pices to the puzzles.
We are put upon this earth and asked to sort out the chaos and madness around us, yet the tools we are given may or may not be defective. How do we know this is a real world, or is this just a world that we create for ourselves? Do other minds exist, or is the idea of being an individual an illusion? At our level, the actions of others seem chaotic and messy, but when we change perspective, what was once random now makes sense. An example would be viewing our actions from a historical view, or seeing how people move from a birds eye view.
Patterns emerge in the chaos, and the world begins to make sense.
Well, enjoy your Saturday. Listen to the Kingston Trio.