The mathemagician has a riddle:
To count on me you can depend,
But count me and you’ll never end!
but preferring to make things more confusing, he adds this, by way of some examples:
I’m hidden in the weights, but not the scales,
I’m there amongst the stones, but not the pebbles,
I occur in this event, but not the others,
I’m in the moon in ether, but not the sun in formaldehyde.