A horn is made of keratin as are hooves, thus as magic is focused through an alicorn to perform Unicorn magic, a small form of magic must also transfer though Earth Pony hooves. This being the tactile telekinesis that allows they and all MLP to manipulate delicate things with seemingly blunted hooves. With further study an Earth Pony might find an ability to focus magic through their hooves. Though I think the alicorns natural focusing shape makes the use of arcane powers, more potent and directed through unicorn means.

Pony are generating or tapping into magic and the keratin is the conductor for the use of magic. Those with more magical ability can see this buildup literally coming forth in wild spells and sparking horns, as when young TS was nervous at her audition for magic school and her scare from the rainboom opened the limitation, and her magic flowed out uncontrolled. Even as she used her gift against the Ursa Minor her alicorn sparked as she moved the creature back to it's lair.

Now as Pegasus wings also contain keratin strands, so they also have the properties of this natural psionic magic, focused upon flight and extended manipulation of objects while in flight. As with the magical wagons that pegasi can fly through the air without the pull of gravity offsetting their use. Also it can be said the psychological focus of the flight magic is also taken into account, with the confidence of RD allowing her to achieve a sonic rainboom, and the less confident FS taking a more grounded lifestyle. They focus through the wings for this magical form of flight using negation of aerodynamic principal, as well as overcoming the needed physiological mechanics if such a being had to perform these same mechanics without magic. Guiding this magic is from flapping and without the wings being used in the controlled motion of winged flight, the magical focus is also not achieved. As in, they don't flap, they don't fly. Horn, Hoof, Feather Magic.

The pegasi have the natural ability to walk or lay on clouds like they were solid ground. This gives us a more of an idea about how their magical telekinetic gifts work. A tactile spread of the hoof touch, that allows all pony to use hoof like hand, is transmitted to to the nigh intangible clouds, infusing them with a localized magic solidity in the area that is walked upon or making contact to pegasus body. An observed ability to create gales of wind are another specialized focus of TK gifts, wherein they have the belief that they can move clouds they touch with a breath, and the focus point magic is making this occur. Also the manipulation of precipitation or the creation of lightning/thunder also seem to coincide with the pegasus weather teams physically touching, using their created winds. As an example of lighting/thunder RD giving a small cloud a kick created the ionic charge magically that sent down a bolt and clap.

Now this may explain Pinkie's ability to break the supposed 4th wall(or at least perform feats beyond her Pony kin) Her ability to focus her pony magic though her mane and tail, as discussed in how her psychological states are expressed though her hairstyling, could exhibit a conduit for her to use magic in a massive, yet unconscious way. When determined, she can move as fast, or faster, than RD. When overjoyed she can manipulate spacetime to tout the wonder of making cupcakes. And other feats seen throughout the show.
Yet upon a depressive state her ability is diminished towards psychological manipulation of inanimate objects to project personality traits to the point they can take a life of their own. Yet upon returning to her happy state of mind the projections are broken and she regains the frizz.

Take into account the Pony ability to use their tails(another keratin expression) in a manipulation of physical object. While not as extensive in use, pony like Rarity have grasped objects and moved them about through another focus of these innate psionic gifts. Then pony like Pinkie Pie who have psychological states of mind literally expressed though the styling of her mane and tail, from depressive limp to the happy cotton candy bounce.


A side thought observed by the Earth Pony, mainly Applejack, is how she is able to nearly perfectly buck apples into her carts with a kick to her trees. Now one could say this comes of practice, but as the hoof is involved, I look at this as another use of magic through the keratin focal point from the very first post. She was still able to somewhat manipulate the fall of the bucked apples even in her unfocused and exhausted state, lending wither a manipulation of the falling apple probability, or a directed transmission of how the apples should fall when released from the trees by the force of her bucking.

Mind and body working as one, and using the focal points of hoof, horn, hair and feather. Magical wands from the earliest human histories of "magic" have mostly been believed to create a 'cone of power' or a focal area for the good/bad will of the caster to manipulate their environment. This cone of power, most expressed by the unicorns shows why they have the most affinity for magical gifts of the pony breeds.

Part of my theory connecting the keratin focus of pony magic and the subconscious can also be observed in the story of Rarity finding her cutie mark. She was literally led by the horn by her subconscious casting of the gem finding spell when she most needed her inspiration. Her magic picked her up, cast itself and led her through the air to her fabulous needs. No matter how embarrassing it looked.

Now look at the Princesses Celestia and Luna, they have the Alicorn, Hooves, Tails and Wings, and the level of magical manipulation their part reaches the levels of goddesses. This alignment of ability connected with respective celestial elements as the rotation of the very planet. Though this event will occur even without the manipulation of the two, such as the continued rotation allowing nightfall on the land, even as Luna was banished to the moon. But again this could be explained as they decided upon the division of duties between night and day and both have the power to affect planetary rotation beyond their respective hours. Celestia continued both shifts bringing night and day for the length of her sister's punishment. Observed when Nightmare Moon made it always be night through her rampage.

I also think the hoof bracers, necklace and crowns observed by the Royal duo are helpful in maximizing the use of these abilities as they seem to always wear such items.

But that's another theory set.