I have a question concerning traditions and spirits. Why do they list the spirits of the tradition to a spell type? What sort of connection is there between the two?

Here is an example. With the Hermetic Tradition, it lists the following...
Combat: Fire
Detection: Air
Health: Man
Illusion: Water
Manipulation: Earth

Why? Am I missing something here?

Spirits can only perform magical services on a spell of their sphere.

Ah, I see! So you mean, if I want to use "Aid spellcasting" on a spell, I need the spirit to be from the right type for my tradition? What about with Spirits of Man. In optional powers, it say they can learn a spell you know upon it's first summoning. Is that limited by their school?
(ie: Can I have a force 3 spirit of man with stunball, and then summon and bind another spirit of man with heal?)

Spirits of Man can learn spells of any type, as long as the summoner knows it.

Thanks Zormal.

But even spirits of Man can only "Aid Sorcery" on the one area in their sphere. So if you were a hermetic mage you could summon a spirit of man that could cast "Powerbolt" (assuming you had that spell yourself), but it would not be able to aid sorcery on a powerbolt that you cast.

The real mind bender will be when you see another tradition has the same spirit working on a different sphere of magic.

Hermetic has Fire for Combat. Another tradition might have Fire for Health.

The school association is tradition dependent. What another tradition does has no impact on what you can do with your magic.

@darthmod: It's becomes even more bendy if the spirit is say Fire: Combat and get's banished and taken over by the other caster who is Fire: Health.