Great Old One
In 4e there is no magical/non-magical distinction in this mechanical sense.
You mean, apart from the fact that there are power sources, which are clearly typed as magical and non magical ? And this, from the Player's Handbook:
- Arcane: Drawing on magical energy that permeates the cosmos, the arcane power source can be used for a wide variety of effects, from fireballs to flight to invisibility. Warlocks and wizards, for example, use arcane magic. Each class is the representative of a different tradition of arcane study, and other traditions exist. Arcane powers are called spells.
- Divine: Divine magic comes from the gods. The gods grant power to their devotees, which clerics and paladins, for example, access through prayers and litanies. Divine magic excels at healing, protection, and smiting the enemies of the gods. Divine powers are called prayers.
- Martial: Martial powers are not magic in the traditional sense, although some martial powers stand well beyond the capabilities of ordinary mortals. Martial characters use their own strength and willpower to vanquish their enemies. Training and dedication replace arcane formulas and prayers to grant fighters, rangers, rogues, and warlords, among others, their power. Martial powers are called exploits.
There is also a Detect Magic: Skill Check right in the Player's Handbook: "Detect Magic (Trained Only) Your knowledge of magic allows you to identify magical effects and sense the presence of magic."
So no, sorry, there is clearly a mechanical distinction of what is magic and what is not, spells and prayers are magic, exploits are not.
This is part of what pushes the fiction of 4e D&D in a more romantic/mythic direction (I mean, no one in The Iliad thinks that the way to kill Achilles is to get him into an anti-magic shield).
This is the way you wish the rules were written, but they are not, see above. There are games/worlds where there is a continuum, from purely mundane to apparently magical, magical and then divine, for example Runequest / Glorantha. I love this, it is so imbricated together that fiction flows naturally from rules.
4e is not built that way, as demonstrated above, the powers and the classes are tagged by their power source right from the ground up.
Note that it's cool if you play it more romantic/mythic, I would probably love your games, but the system is extremely mechanical and not built that way, including specifically the combat which is the most mechanistical in all the history of D&D. You might not want to get Achilles into an anti-magic shield (which would be pointless since his power source is martial anyway), but you will want to slide him 2 squares into a pit. For me, that is the summary of fictionless playing.
Of course, you can dress it up better narratively, but because you start from something more mechanical, it's for me harder than with a system that is more open and descriptive, using for example Theater of the Mind, like I did most of the time before 3e.