During Chargen one of my players brought up this question.
Given a mage uses Detect Enemies (Page 286) near an unalerted guard. The guard has currently no hostile intentions towards the mage (he isn't even aware of him), so I read it as the spell wouldn't detect him.
But in the very same moment where the guard will see mage he will immediatly turn hostile (just assume it is a clever guard). So one could argue that the guard has a passive hostile intention towards the mage, an argument that he is detected with the spell.
Are there any clearer rules or am I creating a situation from nothing here?