Imagine two people, one is afraid of spiders and the other likes them. You subject them both to the same conditions - you make them hold the spider in their hands. One will feel fear and might suffer some long lasting effects from it - some people develop really strong phobias when subjected to such a stressful event, but the other person wont really find the experience significant.
If you define "experience" as what they felt - then you can dismiss the second person, since there was no significant effect on him and you can place a very high significance on the "experience" of the first person. But in reality, they experienced the same event - having to hold a spider in their hands.
And if you, the researcher, didn't understand why it had such an effect on one person and not the other, you might consider that something else must have happened to the first person - something "special" must have occured. In my opinion, that's what you are doing.