We are born with magic. It runs in families but can appear randomly in Muggles as well. Most aspects of magic require the ability, however some do not. Astronomy is the same irrespective of magical ability. History of Magic only requires the ability to stay awake. Potions making does not require any wand-waving or incantations, only precision, patience and skill. Some of the more benign magical animals could be handled by anyone. However, things such as transfiguration and charms does require magic.