[Further points to ponder – Is Magic a psychological, physical or spiritual power. Logic would dictate a blend of all three, or perhaps some sort of bonding power between those elements (bear in mind the need for one to visualise, understand a spell and preform the correct physical movements to elicit a physical or other reaction). Understanding this is the key to understanding many of these questions, particularly those involving magical theory and perception]
I always saw the spells and magic in general similar to kinyanim. A maaseh kinyan (spell) can lead to certain results, but in order to give the koichos to the kinyan, you need kavanna from the poiel of the kinyan. (Not working with the shittas that the kavanna is the main power in the kinyan, which is how I understand wandless magic like Dumbledore and Quirrell.)