There are various roads to learning magic -- each allows the mage to invoke different spheres and has a different flavour of magic.
Any character with the appropriate requirements can learn to cast magic.
Each school of magic has its own flavour but different people casting spells from the same spheres of magic will end up with exactly the same results, mechanically.
A priest of war may call divine fire to to destroy enemies where an alchemist uses precise gestures to summon the essential form of fire, but both are just using the Invocation sphere.
\subsection{Multiple Paths}
People can pick up different Paths of Magic by simply fulfilling different requirements.
If someone has access to one sphere of magic through multiple Paths and has bought access to the sphere, then learning the same sphere through the different Path simply requires some \gls{downtime} and study but carries no \gls{xp} cost.
If a blood sorcerer were to learn the Aldaron sphere as a natural knack and later decided to become an adherent of \gls{naturegod}, they could channel the magic through divine means or through her innate abilities.
All that is needed is a little time to pick up an understanding of how this same magic works through a different lens.
If someone begins as a Blood mage with Aldaron 2 then later learns Song Magic, they would be able to cast Aldaron through Song magic with only a little practice.
In gaming terms, the first \gls{downtime} grants full access to all spheres from any secondary Path.
However, the opposite is not true.
Those on the Path of Song learn spheres easier than others, spending 5 fewer \glspl{xp} to purchase a sphere.
If a sphere has not been `fully' paid for then the remaining \glspl{xp} must be spent to use that sphere on a different path.
Casters never gain \glspl{mp} for learning a sphere on a secondary Path -- whichever Path would grant them the most \glspl{mp} is the only one which counts.
