Obviusly discernment is called for, but I don't fully understand the process nor do I have that gift (sometimes I can tell and sometimes I can't). There are other passages in the bible that blur the issue.
Catholics depend on the church to discern these spirits or manifestations. I used to, but there are a couple that have been approved that I serioualy question, so it's back to square one for me.
I still want to believe that Lourdes and Fatima are true and worthy of belief. Certainly there have been any number of healings at Lourdes and I've also read of one at Fatima. What perplexes me is that evidently even these kinds of healings used to happen in the ancient pagan temples, as evidenced by ex-voto offerings found by archeologists (don't know where I read that, but I did).