Have you ever seen a ghost?
Try as I might, I never have. But I know others who did, and quite possibly the lack of a similar experience prevents me from getting too caught up with those stories.
Despite such distance I don't know of anyone who has 'seen' Richard III or Napoleon or Beethoven. Those second-hand tales involved friends and relatives, but the question can be raised nevertheless: why are the perceptions always about familiar figures, someone already known to the person in some way or form?
As a prerequisite there would be the ambience of the moment. A bit of mystery, some irregularity of the setting, the predisposition of the witness inviting the unusual - but all within strict bounds.
Deconstructing the scenario we find a particularly configured mindset and its counterpart, the surrounding atmosphere. This functional template, this recipe if you will, can be applied to other situations not normally associated with the 'supernatural'. The effect is similar in principle, that is to say an affirmation of what has been expected found in the perceptive result.
An astral shape confirms one's knowledge of history (general or personal), fits satisfactorily into the moment, and reinforces the cognitive processes leading up to that point. On a more mundane level the stance of a person relates to what is already known about them, does not unseat one's expectation, and confirms what one thinks would have happened anyway.
I remember something that took place a long time ago. A birthday party was held in my honour and when it came to leave a driver was waiting to take me away. As I was getting into the car it began to move immediately with the door still half open. A small boy came running to shake my hand but the crowd pushed and he was hit by the door. Nothing serious, we were hardly moving and looking back the boy seemed fine. Still, we didn't stop, no-one bothered with the child and with everybody waving good-bye their body language did not relate to the mishap at all. Why?
There was the festive event, the guest of honour. There was the show of goodwill, all the gestures produced to underline its intent. An accident occurred, too small to shift the seat of common perceptions. Under the circumstances I was not expected to halt the proceedings, a series of events requiring their start, middle, and end. Stopping the car would have stalled the closure as well.
Again, a functional template acted out according to plan. A diversion would have changed the frame, rendered the entire episode unfulfilling for all concerned. And so we drove off.
Observe society and a whole set of such scripts become visible. From revolutionary upheavals to elections to weddings to passing-out parades to the morning coffee, they all follow a pre-defined direction that everyone follows.
Because that's the point: regardless of the joy or the anger on offer, it seems the familiarity of the outcome is more important than the sensations along the way.
We are not automatons, so we keep telling ourselves. Yet in a very profound sense the evidence says otherwise. In classical Greek tragedy the players are being pushed towards their inevitable demise, an end everyone foresees and so expects. This includes the hero, but such is the path its very profundity does not allow the slightest diversion. To turn away would make a mockery of the noble mind, and only when in tears do we truly understand greatness.
How sad.