The Metaphysics of Magic.

While J.K. Rowling never delved deep into the ‘metaphysics’ of spells, we can more or less hypothesize how spells work. There is a (more than) reasonable amount of consistency in how spells are used and how magic works in the Harry Potter Universe.

By observing the interaction between magic and wizards, we can reasonably deduce the following recipe for using magic:

Words + Actions + Intention = Magic

Here,

• ‘Words’ refers to the phrase used for a spell or the incantation. For example, “Expecto Patronum.”

• ‘Actions’ refers to the maneuver a wizard does with their wand (or even the channeling of the magical energy using the wand).

• ‘Intentions’ is pretty self-explanatory.

Let’s look at this with examples.

• One of the most famous magic has to be the levitation charm. It is one of the most basic forms of magic (as is evident by the fact that it is taught to first-years). The three components of our magic formula are perfectly demonstrated by this charm. A wizard has to use the words Wingardium Leviosa, act a “swish and flick” with their wands, and know that the intention behind the magic is to make objects levitate.
  

• In The Goblet of Fire, when Harry was faced with the Hungarian Horntail (dragon), he used a spell to call his broomstick. He said the words “Accio Firebolt” while holding his wand. Thus, he used ‘Words,’ (loosely) ‘Actions,’ and knows that he wants ONLY his Firebolt, thus having ‘Intention.’
  

• The last example is a little darker compared to the previous two. In The Goblet of Fire, Barty Crouch Jr., disguised as Professor Moody, told the students about the three Unforgivable Curses. Referring to the killing curse, he says to the students, "Avada Kedavra is a curse that needs powerful magic behind it – you could all get your wands out and point them at me and say the words, and I doubt I'd get so much as a nosebleed." Here, ‘Words’ and ‘Actions’ are easily recognizable, but the ‘Intention’ is not. It isn’t clear what Barty was precisely referring to when he said that the curse needs “powerful magic” behind it. He could have been referring to a wizard’s experience just as much as to a wizard’s actual intent of causing harm. However, this is clarified in The Order of the Phoenix. During their fight at the Ministry of Magic, Bellatrix told Harry that “you need to really want to cause pain – to enjoy it,” referring to the Unforgivable Curses. Thus, effectively telling us that there needs to be a true intention to cause harm.

Now that we more or less understand how magic works, let’s see how the things I have said above aren’t true. There are various examples throughout the series that don’t follow the Magic Formula.

There are many instances of wizards using spells without uttering any incantation, i.e., non-verbal spells. The use of non-verbal spells was an important plot point in The Half Blood Prince. Usage of wands doesn’t seem to be a necessary condition either.

To understand this, refer to The Prisoner of Azkaban, where Harry ‘blows up’ Marge Dursley. Here, magic happened without the use of spells or a wand. Or refer to the incident when a young Tom Marvolo Riddle, who didn’t know that he was a wizard yet, told Dumbledore that he could make bad things happen to people. Moreover, House Elves and Goblins have been known to use magic without the use of wands.

Thus, we have established that neither incantation (Words) nor wands (Actions) are necessary for magic. The only thing that we can be certain of is that magic requires intent. Harry wanted something terrible to happen to Marge Dursley for insulting his parents. Tom Marvolo Riddle wanted to cause hurt to people.

So, then what is the use of spells and wands? I believe that they are mere tools that enable wizards to perform magic easily.

Standardized magic spells and practices might be helpful in teaching magic to students. It might also be a great convenience to the Ministry of Magical Affairs who has to keep all the wizarding activity in check.