[sub]All types of pony have magic, as has been confirmed; I've just been thinking that maybe, it's all the same magic? That is, it all comes from the same source, a generic power supply that all ponies possess. Unicorn magic comes out through the horn, which is close to the brain and therefore can be recognized and controlled easily by mental effort. Pegasus magic comes out MOSTLY through the wings, allowing them to fly, but also partially through their body, letting them walk on clouds and so forth. Their magic is a semi-autonomic system, like breathing: it can function without their conscious control, and they can also control it (say, to go through a cloud rather than landing on it). Earth ponies have no organ through which their magic manifests, so it simply builds up in their body (making them stronger and tougher) and "leaks" into their environment to have effects on plants and animals nearby.
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This "leaky reservoir" theory is corroborated by a few different things. First, Fluttershy. She seems to have weak pegasus magic, since she had trouble learning to fly, but perhaps it's her wings that are weak: if she has limited ability to express her internal energy that way, then it builds up inside her as it does for Earth Ponies, and thus gives her her ability with animals. A second proof is what happened to Twilight. Her magic seemed to be very weak, then instantly become very strong, which doesn't make much sense: however, if the internal power was the same, and it was simply her ability to express it through her horn that was somehow blocked, the sudden surge of power makes sense.
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This reinforces the impressiveness of the Princesses, who have double or triple the drain on their internal power, meaning that they have far more raw magical energy than others.[/sub]
