Yogananda also warned against hallucinations, which may/may not be true imagination or a true spiritual experience.
One thought I have is, if it were some kind of hallucination where you are seeing ghosts or something, it may be truly spiritual but in a negative or dark sense, meaning it's not just something that's not there (what may be defined as hallucination), but it really does exist in the spiritual world.
Yes.. just because we can not see into another realm does not mean that it has no existence. i think u r hitting on another important point here.
Many people have quite an imagination. At what point does imagination become real? We can imagine music and art and actually make that imagination a reality. Some r better at it then others. There is an element of meditation that uses imagination as well. How would we b inspired to meditate if we did not have imagination and faith that there was something to it beyond all the turmoil of restlessness and persistent thought? We often have to use are imagination to make things a realty.
It is quite likely we have just imagined all this physical reality as well. We may have used r imagination to conjure up a reality that does not really conform to the spiritual reality behind it.