How do we account for the existence of numbers? Are there multiple physical things to justify the existence of numbers? How do we know there are multiple existing things?
Come on, look down at the keyboard. What has been typing on the keys (whoops, multiple keys!). Yes, that's right, it was your hands. Now notice you have 2 hands and each hand has multiple fingers, 4 plus on thumb each. This may be ad hoc
but we can't ignore what we see.